My guess at BB's range is two pair (75, 35, 73), straight (64), overpair that doesn't raise preflop (88,99,TT), set (33, 77), top pair + gutshot (76,74), and for donkey equity 78.

I think that observing this range makes it clear that raising is wrong (raising let's him get away from hands that are drawing very slim like 76, 74, and maybe 88,99,TT, and costs you lots against 64 and 77.

I may even play a turn blank passively, as we're basically WA/WB here.