Here's an idea. What about actually relating to each other and attempting sex when you're both sober and out from under any chemical influence, then seeing how that works? I'm not saying you alone need to be the only one to understand. If you have strong enough feelings to be intimate with someone, you both ought to be sympathetic about each other's sexual "circumstances." That ought not to be a hard conclusion to draw.

If you like and trust someone enough to be getting horizontal, then you ought to have enough affection and respect for each other to understand that sex has its less than stellar times, too--and to know that you can up the chances of a better time by bringing your A game to the sack. Frankly, it sounds like the communication between you two is lousy to begin with. I'm not normally this pessimistic, but the more I read, the more I think this thing is doomed. Asking for tips here isn't going to get you anyplace, either. The one you ought to be listening to is your partner.