There definitely is some potential to grow some tropical plants in our area (I'm a few hours north of you), particularly as the climate continues to shift. I think the biggest limitations you'll find are the
water needs and having a plan in place for killing freezes.
https://permies.com/t/31762/books/Book-Review-Grid This is a very large collection of book ratings that members of this site felt relevant. Each title is linked to the
thread with more detailed reviews. Maybe you can find reference material there.
Many tropical plants might be okay with nothing more than a blanket and some nonLED christmas
lights during cold snaps. I overwintered a pepper in the ground like that last winter. I'd be researching each plant to determine if that would be
enough.
This year I'm trying to grow a mango tree from seed, but since it can't handle sustained chilly temperatures (not freezing) I'm going to keep it in a pot a aggressively prune for size. I don't think I could keep it going outside over the winter.
There are some tropical plants which have varieties that will fruit at least as far north as Austin. I don't know the varieties of the top of my head, but Central Texas Gardner had a recent episode that mentioned a fruiting palm, and my mother had a friend with fruiting bananas.
I'm going to give you a link to a nursery near me that specializes in
native and adapted edible for forest gardens in this area.
http://hillcountrynatives.net/ in particular I would suggest browsing his plant lists. Not everything on those lists is tropical, but many of them are. He also goes so far as to have a separate listing of nitrogen fixing plants for support species.
For earthworks, I suggest you spend some time browsing the earthworks forums on this site. Since you say you are in San Antonio I'm guessing you have a suburban or urban
yard to work with. In my
experience, swales and heavy mulching, and infiltration basins can all, with careful planning, be used without offending the neighbors.