My 2 cents:
I weigh the same as you and have been doing airstyle tricks using a 12m Switchblade for the last couple of years, along with a 133cm board. I ride it in winds varying from 15 to 30 knots. At 35 it gets... uncomfortable.
Most of these tricks require airtime, lots of it. For a lot of them, specially the ones where you're spinning, or upside down, and have just one hand (or no hands) on the bar, having a slower, steady kite really helps. I've had plenty of bad wipeouts because the kite came forward too soon, and it can be hard to tell where it is when you're doing 3 full spins in the air.
As for the sliding, that feeling you had of doing a looooong darkslide with the Switch is gonna be more and more important as you try other slide tricks. On the other hand, you do get used to and learn to manage that extra power during the kite loop, by doing it later (hey, more time for your trick), by pointing the board downwind to absorb the power and even by continuing the loop and turning it into a transition, so that the kite doesn't race through the power zone from one side to the other.
For all these reasons, I wouldn't go with an FX. It's a faster turning kite, and I think it's really designed for riders who want to start with unhooked tricks. I love my knees way to much for that.
Right now, personally, I'm looking into a 14m Apollo as a possible kite to take my progression further. Not sure about it yet, but it looks promising.
Hope that helped! Cheers.