As far as root cause -- I definitely did install that bracket upside down. I torqued to spec, but yep-- the taller part that should have been there went up top and the 1" shorter side went on the bottom. While I did torque to spec I'm sure this is part of the problem.. coupled with the fact that the stud had already been cross threaded by the PO who clearly used impacts to tighten it when doing the bushings. So when I went back to correct my issue, it was pretty damn hard to get the nut all the way off. Had my new nut at the ready, but the bolt itself was the issue at this point.... so when gently using a torque wrench to get the new nut on it must have started transferring to the stud itself and broke it free.

As far as next steps, I had my best friend come take a look-- she's a welder and thinks we can cut into the small metal sheet that blocks the area holding in the nut. It's def a welded nut. Why on earth Toyota went this route is beyond me. But I ordered a new stud and will report back over the weekend how our adventure goes