Not actively pursuing another man seems like a good boundary. Coming up with a good consequence is tough. You could tell her to move out of the bedroom but if she says no, then what? You could try to stop financing her art, but in most (all?) states your wife has legal claims on your income. So if she says no, I'm going to go withdraw money from our account to pay for art supplies, then what? It seems like the boundaries you've come up with could bounce right back into your face.
Your wife's pursuit of the celebrity might end, but the desire in her heart isn't going to go away. She's not going to suddenly fall back in love with you.
You say she sees you as dominating. But you always saw yourself as being helpful to her and serving her needs. I think this is an important point. Regardless of your kind and benign intent, the fact that she's living like a child whose needs are met by a grown up ... makes her feel powerless and resentful towards you. Healthy people go through this resentment process during their teens. They push their parents away and resent them, until they become independent.
That ties in directly with her need to be financially self-supporting. She needs to feel independent. Of course she's going about it in an unhealthy way, but the general desire to be independent is good -- except about 20 years behind most people.
I don't know how you guys run your finances (joint accounts, etc.) but what if you really did start to treat her like a real housemate? Make her to her fair share of shopping, cleaning, paying for bills etc.? I would stop driving her around places too. She has car insurance. If she has a phobia about driving, let her take some driving lessons or get treatment for a driving phobia.
I asked you earlier what would happen if you were not in the picture. Does she have the life skills to be a decent head of a household, take care of your kids? You said she'd be fine. Well, then how about letting her exercise some of those life skills, and empower herself?
Me: 50, MLC/WW 45 Young kids Nov 2015: BD1 Apr 2016: BD2 Jan 2017: W filed Feb 2017: D final