Honestly I feel like on the whole I'll get more use out of these glams than I would out of another set of full armor, and the weapons look fire so I'm here for it.

Honestly same.

You don't need to know every rule or even most rules. Especially in math-forward games, focus on the play and you'll get the numbers in time as long as you're not treating them like something to fear or avoid.

If it helps, many of the original D&D settings were post-apocalyptic to begin with - they had a modern world with elves and magic alongside everything we have (or at least everything they thought we'd have in the 1970s-80s) that was in their past, not their future, so I think modern AUs have room.

Lorefinder isn't bad as a bridge between the Gumshoe system's investigation system and D&D/Pathfinder, though I think Gumshoe's potential as a fantasy-mystery game really gets realized in the later Swords of the Serpentine.

You might try a game like Beyond the Wall or Vagabond, which has a bit less intimidating format and runs a little lighter on math/rules but has similar mechanical roots to modern D&D, they tend to be a lot more accessible and good for easing in for new players. I hope you find something that works!

My character is pretty expressive with her tail and ears especially. When RPing, I find I try to use those to convey positive emotions more, since I feel like a big grin on a hrothgar might be more of a threat display.