Well, as to the swimming part, the pools are heated to about 85 degrees or so - so it depends on the air temperature. We usually get a cold front that lasts a day or two, then it warms up again (low to mid 70's), then another cold front. So if the day is sunny and the wind is low, swimming can definitely be on the agenda.
Crowds can be very good, if you don't go around MLK weekend. I usually go late January/early February and the parks are very nice crowd-wise. Even last year when the Super Bowl was in Tampa, the crowds were not bad.
I can't comment on the rest of your question, as I stay in the cabins.