Hi again Sandy,
OK, I read your questions again and I see I did not really answer them.
As to what windspeeds would be appropriate for your 3 sails (8.5 m2 Sailworks Retro; 7.0 m2 NP VS, and 6.1 m2 Bic Freeride, my best estimate would be this (based on a sailor weight of around 150 lbs.)
Your 8.5 Retro would be good from whatever your personal wind minimum is to about
14 knots (16.1 mph). If you retune the 8.5 you might comfortably get another couple of knots out of it. So, say 8-14 knots for the Retro.
Your 7.0 m2 NP VS will probably get you planing (I'm not real familiar with this sail so I canot be sure how much low end performance it has) in around 13 knots, but maybe as little as 12 knots, and should be OK up to around 16 knots (maybe a little more with some serious downhaul and outhaul adjustments to depower and loosen up the top of the sail).
Your 6.1 Bic Freeride (I have no idea exactly what characteristics this sail may have) should be good to around 20 knots, and you could expect to get planing on it in about 15-16 knots.
So, you have some significant overlap with your sails, but to simplify your selection process I'd say at under 13 knots(14.9 mph) the 8.5 Retro would be my suggestion, then at a solid 14 knots (16 mph), rig the 7.0 m2 NP VS.
When the wind is a solid 16 knots (18.4 mph) you can rig the 6.1 Bic Freeride sail.
This is all a bit theoretical, and you may find that you can use the 7.0 m2 in a little less wind speed, but for Florida conditions, I would think being a little overpowered would be far better than being underpowered.
Remember, if you rig too big (within reason) you can always sail a bit "sheeted out" (don't pull the sail down and in as much when you are hooked in and in the footstraps)
and dump a bit of power. Ease your sheeting angle gradually and you won't upset the balance of the rig or your board.
Hope this helps,