Have you read this thread? It might help answer your question #3.
Fruit trees that like their feet wet? - #12 by Ozymandias
I know jujubes like regular moisture, but I don’t think they do well in poorly drained soils. Parts of my yard don’t drain well, so I’ve planted trees on raised beds and mounds, and they seem to be fine. But I haven’t had any flooding for any significant length of time - just soggy soil for longer than I would like.