Wait a minute your in Miami and you actually have soil in your yard and not coral rock after 4 inches of depth, lol.
I imagine you did shovel lots of rock.
The pond looks great and after several yrs you will notice that your platies breed darker and darker which kinda stinks but the outside platies all do that.
As the saying goes when it comes to Bufo toads and Cuban treefrogs " If you build it they will come".
What type shrimps are those ? They are very pretty.
"high pH but the falling and decomposing leaves should balance it out"
It doesn't matter as far as fish go, if you go by the canals you see Oscars,jaguars,Mayans,red devils,jewels and they breed.