Yeah, that's fustrating, but the guy shot 31 3-pt shots in two games. Sometimes guys go cold. It's not like your guy is a lights-out shooter, either. He's ok, probably good at D3, but not good enough to be shooting that many. Plus, while he's pretty athletic, he's not very fast, and probably doesn't have the easiest time getting off a shot, even with the good BH.
If I was you, I'd be happy that he's made as many threes as he has and dial it back a bit. I've had guys who should have been a lot better than your guy shoot the same percentage at (0) or even (-1).
So while it is extremely frustrating, especially against the (-5), I think you should at least acknowledge that you're setting the guy up to fail, at least in games when the shooting RNG isn't going your way.