Welcome back! good info to work with, thanks. So the Blast would normally be a good board for you as you have quite a few of the skills that it's intended for. But as you mention mainly light winds, combining foiling and you want an easy ride - the Gecko Foil 135 may actually be the better board, especially in the pretty light winds you mention. It's the better of the 2 boards for foiling, being longer and with a wider nose. Also the better light wind performer due to the extra width.
The Blast is a great board for "blasting" around, is narrower in the centre and therefore feels more sporty/performance oriented than the Gecko. The Gecko has a wider centre/narrower tail for easy planing and easier gybing, so it's a great board to start on again and perfect the skills of gybing etc.
Sails I'd recommend Duotone EPace/Etype or anything similar from other brands in no cam, for both of those boards. I guess for those winds/your weight:
Foil Flow 1500 (our best allrounder) + Gecko 135+ 7.8 EPace (you could take the foil sail, Ftype, but then it's not as good for using without a foil)
Gecko 135Foil + EPace 7.8, possibly a 7.3 if winds get over 15 knots - this will work for normal windsurfing too?
Hope that helps, let us know if anymore questions!