I'm not Emily Post, but I think on the scale that hits about an 8. Unfortunately, it sounds as if you are ASKING for cash instead of truly not wanting gifts. If people are going to give you something no matter what AND gifts are banned, they will give in the form of cash or gift card. You'll find it in their wedding card to you thereby making the wishing well irrelevant. The only way a 'wishing well' would be okay is if it were for a favorite "named" charity and all the cash truly went there. Otherwise, check the envelopes.
Barely an exception, but it might be okay is if you are banning gifts because you literally have no where to put them - i.e. you live in a studio and can barely turn around already or are joining the Peace Corps right afterward and will only have what's on your back. ;-) Still no wishing well, it'll be in the cards.
The two drink minimum - If you're really not well off, most people will know it and I think it's okay as long as people are aware of it AHEAD and WHY. It allows people the drink to toast the couple, etc. After that, their buzz is on their own. Not great, but not everyone is rolling in money.
Good luck on you new life together!!