Don't be sorry for the post - you are getting your thinking out there, in black and white. It's easier for you to see that way.
You say that you aren't sure what she wants, but I think she has told you. Not so much a "replacement daddy," but a partner to walk through life with - and her life involves a 12 year-old boy.
If you don't want the same thing (and this is where I think you need to reflect - what do you really want?), then it is not a good match.
You might be feeling weird about it, simply because of how quickly she involved you in her son's life. Really wasn't fair to the boy to get to know you if neither of you are sure if you are a permanent fixture. Could she be playing on your guilt over that, pressuring you for more than you want to give?
