I know how you feel. I am also a light sleeper and he falls asleep instantly. He doesn't snore too much, but when he does I'll either turn over or nudge him in some way and that usually makes him stop. He snores worse the more exhausted he is (or the more he drinks ).
You could have him try those breath rite strips that opens the nasal passage. An ex-boyfriend from years ago used those and they worked.
Otherwise, I go sleep on the couch.