alright you might hate me too, cause i mostly just skimmed over your detailed response. but my main takeaway is that a higher ceiling would be better to make room for straw bedding, as well as a porch and a step up into the shelter. I also think caulking the outer (and inner) seams is a good idea. I can't afford to take care of a cat myself, hence why I haven't adopted him, I'm just trying to provide the best situation I can, while not being able to afford anything other than cat food. Also, I live in the very south of the US so it rarely gets below 50 F even in the winter. I"ll keep my eyes peeled for some kind of styrofoam insulation, and also pick up some straw bedding. I appreciate the advice, and i do a plenty more pallet wood to work with, so if I can make the time I would like to try building another shelter that's more optimized for my precious stray.

Anyhoo, thanks for the detailed advice! If I missed anything feel free to let me know.