You didn’t say what state you live in, but chances are that it’s a community property state. So that money, which is “yours” and “his” now will be both of yours if you marry. You need to think about that, and so does he.
A mindset of one partner “against” the other is *not* going to help you set up a well-functioning marriage.You also need to think about the benefits vs. costs to the relationship of giving ultimatums about $3000 rings (and things in general). Ultimatums and name-calling (“cheapskate”) seldom lead to the compromise and problem-solving that are necessary for a healthy relationship.I also suggest you give some serious thought to your financial relationship with regard to housing costs and support of your son. Make sure that you and your boyfriend are in agreement on this before you undertake the commitment of marriage. It is only fair to your son that all three of you understand one-another expectations for how the responsibilities and privileges of financial financial support, childcare, discipline, and emotional support will be shared. Ideally you and your boyfriend will agree on the major points — if not you need to resolve any major conflicts *before* you marry.
You may find per-marital or relationship counselling helpful in dealing with such issues. I also suggest you look at some relationship books to help you identify which issues may lead to conflicts. (Unfortunately I can’t think of any titles off the top of my head — can any other netters out there think of any good books?)