Sure! OK, so I finally got a perfect result I'm happy with, but I'm going to play with it more before I post to that thread. I think it was just another case of me being dumb. I'm using the "Standard" shader with the "Cutout" Rendering Mode--the fatness/weirdness of the wooden bars were due to Alpha Cutoff being set to 0 (I progressively feel more like an idiot the longer this thread lasts, haha, the DEFAULT is .5, not sure how it got set to 0). I set the Alpha Cutoff to x >= .5 and it renders perfectly. I can't use unlit since I have a day/night cycle in the game, and the light adjusts accordingly.
I combined this with the technique posted about in the other thread describing the GIMP script that automatically spaces and margins the tileset and I get zero bleeding / perfect rendering. I'll post all the stuff I learn about the Unity workflow after I finish one full asset and I have a bit more experience in this--I don't want to post something incorrect. Thanks again for all your help and for making this and sorry for all my stupid questions!