1. The relationships do get past the point you are in. It is different for everyone. There are couples here with dolls; some with a threesome relationship, some not. The important thing is to find what works for you. The most important thing is to communicate with each other. Regardless of how the doll looks, there will always be things you can and positions you can get into that the doll can’t. You respond, react and initiate. The doll cannot. Explore her together, be intimate with each other and phase her in. Whatever works for you!
2. It’s very unlikely that he prefers the doll over you. It’s great that you want to get involved, too. It can be hard for women to understand that guys can have sex without getting emotionally attached. It’s a biological urge we just need to take care of. We can masturbate to other women or use toys/dolls to get off without getting emotionally attached, and come back to our girlfriend/wife and love her the same as before.
We can even have sex with other live women and not get attached, but the risk of developing an emotional attachment in an affair, and the risk of diseases makes it against the rules of most relationships, understandably.
Just give it some time, and make sure you communicate your feelings to your partner. Be patient with each other and your relationship could grow even stronger in the end!