I'm trying to keep both my soon-to-be-ex wife and my gf happy
Why try to keep both happy at the same time?
My soon-to-be-ex wife will stay with me if I reconcile with her.
It sounds like you might want to stay with your wife, so you need to decide whether you want to stay with your ex or be with this new girl you got. Trying to juggle both will lead to you having neither.
I have to have them both.
When you enter into a marriage, you are agreeing to be loyal to your wife, so I'm afraid that you cannot have both. Your wife will divorce you if she finds out that you have a girlfriend, so you have to choose one or the other. It sounds like reconciling with your wife might be your best bet.