Crying? He has reached chronological adulthood, and he's crying because you're not drinking the tea he's pouring? I don't think this prospective mother-in-law is the only one who has to have things her way, or who is willing to use emotional manipulation to get it.
There is no single correct way to deal with one's relatives. Your way is not the correct way. His way is not the *correct way. His mother's way is not *the correct way. There gets to be a point, though, where someone who keeps doing the same thing and yet expects either a different result or sympathy needs to realize that, as the saying goes, "that dog won't hunt."
You can help another person make their choices by helping them see alternatives or ways of looking at things that they hadn't thought of. You can give encouragement to a person who wants to do something differently, yet doesn't feel capable to make the change. You cannot train an adult who does not want to be trained. Do not allow yourself to get any older before learning this rule.
If you can't live with what he has forged as a relationship with his mother for the rest of your life, fully knowing that it is at least as likely to get worse as to get better, then cut your losses right now. How he deals with her is his decision to make. You cannot make him do it differently.
Some couples can live with "your mother, your way, just leave me out of it entirely." If you can live with that, if only he would agree to handle those things that he wants to handle totally differently than you would without whining to you about his results, then say so. If he wants carte blanche to do things his own way, though, then he is not entitled to emotional support, financial support, or any other kind of support from you. He might get it, if you decide to give him that, but he is not entitled to it.
IMHO, you never just marry the one person. You marry the whole family. I wouldn't marry someone who didn't have a mutual respectful and healthy relationship with his mother. I say that as someone who has had her MIL living in the same house for over ten years. Look for someone who treats his mother as you want your husband to teach your children to treat you. It is well worth the wait. Actually, it is priceless. Resolve to only marry a man whose mother is a gem. You will never regret it.