The answer to your question about who you should date and who you shouldn’t date, has more to do with you than either of the two men. You have to figure out what you want. It sounds like you want to have a marriage or a long term, committed relationship with a man.
Since you dated Mr. A for 2 years, and didn’t really get a commitment from him, I’d seriously question his intentions. In addition to that reason for not continuing with Mr. A, after you broke up with him in August, you took him back again, and broke up shortly thereafter because you couldn’t stop thinking about Mr. W. If you dropped him again so easily, I just don’t think Mr. A is going to be Mr. Right for you!
However, Mr. W has been very upfront with you that he doesn’t want a relationship right now, so I think you have to take him at his word, and rule him out.
Neither one of these guys is worth your spending any more time on because neither one is right for you. Get back out there and keep dating until you find Mr. Right, but don’t waste your time with men who aren’t going to be that guy for you.