I know the feeling pretty well...a few things it might be, or might help (and btw, I don't see how it could be the board doing much to cause it if you are on foil)...
Like
@krixikraxi said, not having an athletic stance may be part of it, and especially if you start leaning back, either with more back foot pressure and/or with your hips back, then all sorts of things can go wrong to try to keep things under control, including breaching...so...athletic stance - weight balanced with adequate front foot pressure...(I cruise with pretty straight legs, but when it's getting crazy, I've got knees bent and ready for anything)
...And you might work on just willing some confidence and get used to going faster, lots of falls in lots of sports happen because we get freaked out and nervous and make mistakes...
Also, not only to avoid breaches, but to make the foil less sensitive to wave energy at the surface, you might ride a little lower on the mast...that can make for a less bumpy ride, especially with a lifty foil (not sure if that is true of the SAB R990).
And with the wing??? I don't know but you may be inadvertently sheeting in a bit to compensate for hips back, and/or lack of balance, and/or fear (I can imagine hips going back, then pulling in on the wing, then your feet pushing the board forward out from under you?!)
Getting comfortable being overpowered is super important, as its part of the game...
BTW - what wing are you using, and are you sure it's adequately inflated? My first wings were a total handful overpowered, the new stuff is so much better for me and I feel I can adequately depower however much I need.
Good luck!