Dude. Is she 13 years old? If not, she may as well be.
You are addicted to this woman. There is absolutely nothing in this relationship that benefits you, and everything that hurts and drags you down. Does any of it feel familiar? The dynamic or the person? Anyone from long ago? You may want to close your eyes, try to relax, ask that question and see what bubbles up.
As for your wife, yes wife; she is not your gf, it’s a legal fact. Stop playing make believe. It’s terrible for your mental health. It sounds quite unlikely that your wife has any desire or capacity to change. There is absolutely nothing you can do about that.
Let’s take a look at her character: she was quite willing to take your money. She sure didn’t mind your buying furniture for her apartment. She was screwing around with her ex while being involved with you. But, anything to do with reciprocating your love and affection is repugnant to her. Oh, she’ll put on an act from time to time, to ensure that you stay hooked in. And that is exactly why you are so locked on to this woman.
In the field of Behavioral Psychology, there is a concept known as intermittent reinforcement. Think of slot machines in Las Vegas. You put your money in, nothing comes out. Do you just walk away and go back to your hotel room? Not likely. Most people will give it another try. How many tries they’ll give it is an individual thing. But, the point is, people generally don’t get discouraged and quit the first time a slot machine fails to deliver.
Now, think about a soda machine. You put your money in. Nothing comes out. Now what? A lot of people will give it one more try. Nobody is going to stand in front of the machine, pouring money into it with no soda coming out.
Yet, being glued to the slots is a Vegas staple.
That is the power of intermittent reinforcement. You’re willing to keep playing the slots because you know the reward could come at any pull. You won’t play the soda machine because you quickly realize that no reward is coming.
Intermittent reinforcement makes a behavior very difficult to extinguish. The periodic reinforcement keeps us repeating the behavior over and over.
Your wife is your slot machine. Every now and then, your attention and affection gets some reinforcement and you are pulled right back in even more tightly.
These types of bonds are very hard to break, but break them, you must. You’re wrecking yourself. I suggest Dr Patrick Carnes’ book, The Betrayal Bond, and you may want to do a little research on Stockholm Syndrome. Breaking this kind of addiction probably requires some professional guidance and support.