I use bronco fly spray and outdoor bug spray for me, too! It keeps the bugs off for a little while, especially if I'm moving, but if I stop to rest in the shade I get bitten! The barn I ride at has a ton of bugs and is heavily wooded, so I just try and get us both sprayed up as best I can. When it starts bothering me or my horse I ride the rest of the time inside!
As far as the bites, I heard putting vaseline on the cuts helps. It protects the bite and I think the bugs won't bite it? You might also want to look into some fly stuff for when your horse gets turned out! fly mask/sheet/etc :) If you put any on the ear just put a tiny, tiny amount because you don't want them to get that in their ear! There's all sorts of fly veils and stuff too -- might be worth a try! I'm sure he doesn't like it anymore than you do!