The way I see it, you have two options. One, go to counseling. I'm not talking about Pastor So and So, or your mama (in fact, families need to be left as far out of marriage business as possible), I am talking about a REAL professional marriage counselor. Most counselors will give you a free consultation (the first session) which ends up being a free counseling session, as they are just trying to find out info about you to develop a program.
A lot of married people run or shudder at the idea of counseling because it is a blatant admittance that you have a problem. Trust me, the counseling WORKS. A real counselor will be straight with you and will let you and your wife know who has the "bigger" issue, so to speak. They will suggests that this person (sounds like it would be your wife in your situation) go to individual counseling to work on some issues as well as the joint marriage counseling. Be 100% honest in counseling, even if your wife is not.
If your wife refuses to go to counseling or is not cooperative, then you need to cut your ties with this woman. She does not care about you, the marriage, or the emotional health of your son. This leads you to your second option. Divorce. Be smart about it though. You have lasted two years, you can last another 6 months to a year. The reasoning for doing this is to set yourself up. Start working hard, even get a second job if you can and it doesn't take too much time away from your son. Cut unnecessary expenses as much as YOU can.
Sounds like your wife is going to spend as she pleases. You have got to up your income and begin hiding money. Get an account that she doesn't know about. Make sure she doesn't see your check stubs, or any indication of how much money you make. Get a P.O. Box and start forwarding your personal mail there. Cut out most if not all of the hanging out and wasteful spending that you do, and save, save, save. Build yourself a little nest egg, but DO NOT let your wife find out about it.
Be as cordial and nice to her as you can so that she suspects nothing. Set up another inexpensive place to live, and start gradually moving all of your stuff there. When you have done all this, hit her with the divorce papers and then bounce. Make sure you have gotten all of your valuables out of the house before hitting her with the papers, even if it requires you to take a day off of work and move the stuff out. Women love to destroy your shit, especially when they know you care about it. This is my advice. The reason for all of this preparation is because if you and your wife breakup, you are going to take the bigger hit (initially) because she makes more money.
You have to protect yourself. Also because custody battles and divorce settlements are long, costly processes that you cannot predict. Depending upon where you live and whatever judge you get, you may end up paying her money in spousal and/or child support, or she may end up paying you. Either way, you will be better off if you have money saved. This will also assure that you are not starting at ground zero going forward with your income. This is my two cents. Suggest counseling and ACTUALLY set it up. If she refuses, or it doesn't help, get out, but get out smart. Sorry So Long.