I think you need to step back and reflect about this whole issue.
Firstly, I believe that all kids should always be with the mom. This is a the natural order of things.
She may not provide the BEST environment, she may not even be a good mom, but that does not mean the kid should be separated from the mom.
you have argued that you can provide a BETTER environment, but that is not a valid reason to separate a mom from the kid.
You probably love her a lot, consider her as spouse. Probably she has lost her feelings for you. She wants her space.
By constantly demanding her attention, demanding for the kid, you are just freaking her and her family out. Your actions will never score any points with her at this moment.
you say you want to be a father. It takes 2 hands to clap.
It's not a unilateral decision.
Reflect on this question, are you being selfish by demanding your right to be a dad?
Just because you treated her well, does it mean she owes you a commitment?
If both of you are available for marriage, I am wondering why both of you are not married before having the kid.
Could it be she (or her parents) wants marriage but you were not keen? This is a common desire of women.
My advice is.. give her the freedom to choose, give her the space she wants, give her the time.
Give her the assurance that you will be there for her as a spouse, unconditionally.
If she or her kid needs any help, she will approach you. That is when you can trash things out with her.
If she's doing ok alone, wish her all the best, and maintain the frenship.
We are all in relationships so that we can enjoy each other's company, we add value to each other.
Relationships should not be about negativity or pessimism.
If she can't appreciate your point of view (whether yr POV is indeed rational or not), both of you are just not meant for each other.
But just keep in mind, over time.. ppl do mature.. and ppl will change eventually.
Give it time, and let it be a natural process.