"That explains why I am on the fence so much. On one side, it does not make logical sense to move in with her, due to our differing finances, freedom, and even desired lifestyle (she is mostly the one who wants to settle at one place and have kids, I am attracted to the idea somewhat but I am not sure I would enjoy it for many years). On the other side, she is pretty special to me and I don't have the heart to let her go, and that is coming from someone who ordinarily has no qualms about breaking up and who is not afraid of being alone (I enjoy being single). If I can explain my feelings, it is a mix of having my single life plans disrupted, being sold something I didn't really want by someone who is very convincing, but also falling back to a life more similar to what I had growing up and enjoying it quite a bit. If I want to ever settle down, she is probably the right person to do it, but the timing feels wrong a bit -- I'd rather be doing that in my 40s and 50s, although that sounds awful for the children."
Words matter. Be honest with yourself if you are blaming her for "being sold" something you didn't want. You are independent and you can "buy" or "not buy." It is rather interesting that you use transactional financial terms to describe the pull of this relationship and I think that it would be good to think about this. Look at the words some of the other posters use to describe their relationships. I am making no judgement, but you may be able to learn what is most important to you and what will make you happy by looking at your words.
It would be wise to tell her this, using the words quoted above. Anything less does not help her make a good decision. She has youth and a womb and wants to be in a committed relationship with children, three things that are definitely part of the equation. You need to put those onto your mental spreadsheet. Those three things are worth money (this is why judges award alimony and child support), and you seem to want to let her give those things to her (although you are clearly ambivalent) while completely protecting your own financial assets. You simply cannot have it all. It seems to me that you look at your previous life (saving your money, earning your money, and not experiencing a loving lifetime relationship) as a life that you really like. That is totally OK; we are not all meant to be in committed relationships with children.
I do understand your position, although I did spend my youth in a committed marriage with children. Now that I am on the other end of life, FIRED and single for 9 years, I find myself reluctant to want to remarry. Disentangling assets is so very costly and disruptive and... unhappy. Even not being married, sorting out possessions and living situations after a breakup is pretty horrible.
On the other hand, I was ambivalent about marriage, decades ago. Even though I am no longer married, I have two wonderful children. The value of that relationship is incalculable. I cannot imagine my life without them.
There are some folks on here who seem insulted on your behalf when some of the posters suggested therapy. Take that with a grain of salt. Some people do not value therapy, and it would not do them much good. For other people, it is a very good investment of time and money and clarifies their goals and relationships. I make no judgement either way.
And, the relationship issues are inextricably tied to the financial issues. That is why so many marriages break up over money. Both are really important, and I think the posters who address both are answering your questions in a relevant way that shows concern for you as a whole person.