I would ditch the north facing panels. According to everything I've read, panels that are much north of direct east/west are a waste of money. Maybe it is different in FL, though.

Seems to me that the if you really are getting 300 sq/ft of panels on a 430 sq/ft pool, you should easily get your pool up into the high 80s for most of the year in FL. (I can't figure out how you are winding up with 300 sq ft based on 4 4x10 panels, maybe I am incorrectly reading what you wrote). I think the year round part is what drives solar installers in FL to add more panels than we would here in NY. That would give you close to 70% coverage, which is generally considered more than adequate.

A good heat pump is certainly an alternative. Generally, it is a bit more expensive to install (if you get a really good one) and it costs more to run, but it may be your best option. There are solar panels that are built directly into the pool deck, one of the forum members has them, perhaps that would work as well.