I believe I positioned mine just to the side of the guard as it's offset. I have a fairly wide plate on my jack. Worst case, secure a 2x4 to the plate just to get it on jack stands...
Not really sure why this is so much of an issue for you, Toyota dif drains have been there in the same form for decades, if it where an issue, I am pretty sure they would have moved/fixed it by now.
Most floor jacks come with a rubber pad, if not throw a block of soft wood (poplar or fir 2x4 or 2x6, you could even use 1x4) on the jack pad, the softer wood will deform to the jack pad and mold to the dif, your not going to mess up that drain plug unless you really screw something up. :noidea: