A Kode 80 would be the most similar to your FSW 78 in planing, speed, and general feel with with SIGNIFICANTLY better high wind wave performance and a more secure feeling at speed.
But if you're also after better turning at lower speed and "bad" waves, a Quad is what I would recommend. And at 88 kilos, I think the Q76 will be small enough even though it's a rather wide board. I think you will be blown away with how easy and effective is is when wave riding.
Sails: It's very individual. I think you will find the 5.7 working OK on the Q76 too so you can then safely go for 5.0 and the 4.5+ smaller if you need. An alternative would be to add 5.3/4.7/4.2 to the 5.7/6.5. The advantage would be a better possibility for fine tuning in the medium wind range. And at your weight the Q76 will after all be a bit more natural with a 5.3 than a 5.7, so 5.3 instead of 5.0 would mean more and better time on the Q76 instead of the big FSW, I figure.