You, sir, are in the exact same spot I was 5 years ago, albeit with a different tow vehicle. Whilst I cannot (yet) offer any 4Runner specific feedback (I just purchased my 2016 SR5 back in Oct, after camping season), I am coming from a very similar vehicle and locale (COS) otherwise.
My tow vehicle was a 2006 Nissan Xterra with a 4.0L V6 at about 4800# or better, 106” wheelbase, churning 265 hp and 284 ft-lb torque thru a 5-spd auto tranny. Honestly, felt like a lot stronger vehicle than the 4Runner: a lot more torque and better gearing. It towed our trailer like a dream! But I digress... I too can echo many of your same concerns, so thought I’d pass along some feedback from my experience towing in the mountains since 2012. We are in our mid-30s and picked up a Forest River Flagstaff Micro-Lite 19FD under $15k (single axle, 2900# dry sticker, 3800# or so GVWR) for our then family of 3/now family of 4 (our boys are 6 and 2 now) and are convinced we made the perfect choice. ABSOLUTELY NO REGRETS!! We bought the trailer for a two week road trip to Mt Rainier (WA state/3k miles roundtrip) our first year and we travel all over the rest of the state each season. We frequent SW CO/Ouray annually, have been to Steamboat Springs a couple times, South Fork, SE UT/Moab, RMNP, Buena Vista, Crested Butte, etc, etc. As you know, plan on climbing some major grades wherever you go. Never once have I thought “boy, wish I had a bigger trailer” headed up or down Monarch, Vail, Wolf Creek, or Loveland (Eisenhower Tunnel) Passes, but repeatedly have thought our V6 SUV was working plenty hard enough and glad to not have anything heavier!!!
I like your spreadsheet/thought process; I had one similar and you have obviously done your homework.
You are wise to keep the weight to about 3500#... that was my target number as well. For me, it was 3000#-3500# dry weight max, with as much cargo capacity as possible, but at least 500#-800# net carrying capacity. If you’ve got full 30-gallon black/gray tanks you are already eating up 500# there alone! That nixed the KZ offering for us (Escape was new at the time, IIRC, and capacities seemed less).
As to your selection criteria, keep to it! They are good, solid “go/no-go” qualifiers and as you know, it really narrows your choices–something has to–but keep them in front of you lest you get sidetracked and regret it later.
1. Dry bath: Good call. Avoid the potential compromise whilst looking for options in the ultralight segment and stick to your checklist. You won’t regret having it later when you have to live with this thing a month or two each season.
2. Bed: A build a bed/dinette convert-a-bed would get old in a hurry, but curious why you’ve nixed the Murphy bed option? We have one, love it, and would highly recommend. We keep the bed made up full time, move it up out of the way when not in use, and have a sofa to sit and relax on, watch TV, sit and read books, etc. It uses gas struts to assist with lifting, so that is easy enough. Essentially gives us two floorplans in one, or at the very least, simulates a much larger floorplan. Where are you going to lounge in that R-Pod? Just food for thought…
3. Sleeping capacity: Tough to find space for 4 in this segment, especially with the fixed queen bed limitation. Enter slides (adds significant weight), tent fold outs (no interest to us), or bunks on some models. We found the ideal compromise–overhead stowaway bunk and convertible dinette. Not much more to say, you have obviously researched and found the options.
4. Hard-sided: Us, too. We were tempted by the Trail Manor marketing propaganda, but talk about an overpriced compromise product. $30k+ for a glorified pop-up… seriously? Having made many, many stops on long roads trips to just hop in the back to change a diaper/soiled clothes, take a potty break, have lunch, or even overnight at Walmart… good choice.
Also, some additional considerations:
1. Fridge: Go as big as possible! We got an unexpected upgrade to a 2-door, 6 cu ft(?) model and it is great! Would not want much smaller for the extended stays.
2. Gray/Black tanks: Looks like most everything on your list is 30-gal; great, max those out, especially if you plan on doing any dry camping/”boon-docking”. We can make it 2-3 nights max with 30-gal tanks and careful, conservative use.
3. Fresh water: This one is a little easier to overcome since you can easily carry spare 6-gallons jugs, but refilling a small tank will get old.
4. Oven: Some may/some may not. We have one and it sure comes in handy, esp. considering your microwave will be in-operable without a generator or electrical hook-ups.
5. Dry-camping: If you plan on doing any boon-docking, dual batteries and LEDs are a must. We burned up our single stock battery over the first few trips not knowing any better. We learned to conserve power, but even still the heater alone would drain a single battery overnight since rule of thumb is to not drain more than 25%-50% of capacity. We now have dual 6V golf-cart batteries and the difference it is night and day! You still need to be intentional, but the safety margin is much more forgiving. Don’t forget some solar power to keep them charged. I put together a 100-watt set-up with a stand for a few hundred bucks. Boon-docking is a whole other, lengthy discussion of its own. We found a great book on the subject and could find the name if you are interested.
IMPORTANT: A weight distributing hitch with sway control is ESSENTIAL EQUIPMENT to making this combo work, IMO. I would not even consider towing without. My Xterra had a HD suspension (OME HD all around, beefed up leaf packs out back with add-a-leafs plus helper springs) and I still squatted a good bit out back. Forget it with a soft coil spring suspension. I heard great things about Equalizer and never looked elsewhere. Stability is great, really ties the vehicle/trailer together, and any sway is essentially non-existent. Passing semis on two lanes, down hills, whatever, this thing is fantastic! Don’t second guess, just do it. I too saw the conflicting info and internet speculation as to whether or not the 5th gen can use a WDH so I contacted Toyota directly:
Also, 2013 4Runner manual eludes to (and thus endorses?) its use:
Other stuff. I’ve got a Prodigy P2 trailer brake controller and would highly recommend. Easy to use and set-up and has a nice manual activation switch… great for a quick check to make sure the trailer brakes are working. I’m adding airbags, too, as my Xterra experience tells me they are going to be essential. I’m on the fence about an extra tranny cooler as I have concerns for it voiding powertrain warranty, not that a roasted tranny is any help to the contrary; think I’ll try it stock for starters and maybe find a means to monitor it. Those ratcheting tow mirrors linked above are the same ones I have and loved them on the X; they are solid, huge viewing area, and very little vibration; I initially picked up my trailer without any… then drove straight to the nearest parts store as I could not see a thing! The rental suggestion is a great thought; check out TrailerWorldDenver.com . This is where we bought our trailer and they have rentals. While not a cheap proposition, it will at least get you in close proximity to one of your choices and what you are in for; just think of it like several nights in a hotel and starts to feel more justifiable.
They also appear to rent with a WDH option (again, I would not even consider towing without!!). The place is off east Colfax and pretty shady at a drive by, but they are good, honest, old-fashioned folks and we got a great deal and had a pleasant buying experience from the family run operation.
Anyway, there is my synopsis, hope it helps. Would love to offer some 4Runner specific feedback, but you are going to have to wait another few weeks for that. I am adjusting my hitch and taking a local test tow in a few weeks, then our first trip is to 11-Mile (Lake George) for Memorial weekend. Good luck with your decision making! Feel free to give me a shout if you have any other regional, trailer, or dry camping questions.
Steve
PS, a couple shots of our much loved and missed Xterra:
http://www.toyota-4runner.org/2665124-post169.html
Now I'm going to be the one horking everyone off. 
