Ask yourself do you want this relationship to survive even if it entails no sex and little expression of love?
Your partner won't change unless he wants to, deep down inside.
Yes, you can try to help him, and if you decide to stay you have a long hard road ahead.
He needs professional advice to stop drinking and to start eating a diet that is healthy, and honestly the advice might be taken from a professional, from you he is likely to feel you are nagging. (You aren't, you are expressing concern and making sensible suggestions, but does he see it like that?)
Sit down and have a long honest talk with yourself, then with him afterwards once you know what you really want to do.
If he won't stop drinking (which might in itself help his erectile disfunction), start eating sensibly and give you some kind of affection in place of sex, then I am afraid your relationship is not going to be any fun at all. I am loth to say, "Get out while the going is good", but it might just be the only option you have.