It's natural to feel sad, happy, elated, anger, distate, numbness, hatred, contempt.
Don't throw in the towel because you FEEL contempt for you wife. That's what she's doing, right? You are basing your DB attempts on the belief that our FEELINGS can change. Don't sink to her level, dude.
Niether of you wants to be "roomates".
Continue detaching and GAL. It will give you perspective. It seems to be working.
Do not ask her "how would you feel about me taking a woman to the timeshare?" unless you plan on having an affair yourself. It will come across as petty and childish. It will also sound like an empty threat intended to make her "think" -- which is what I believe you are trying to do.
If you are planning on being roomates with both of you dating other people, then I think before you do this you should consider getting a divorce. Leave this thing with your honor and integrity intact. Your son doesn't need 2 parents at home both carrying on affairs. Either you "win" your wife back or you divorce her for adultery.
Show him what a real man is: faithful, full of integrity, willing to fight for his marriage and family. And if your wife refuses to stop seeing other men, then show you son that a real man does not accept sharing his wife with another man.
Since you love your son, YOU need to be the rock and moral compass in the family. What will dating accomplish? What are you trying to tell him... Your mom cheated on me, now I'm going to do the same thing?
Is that WHO YOU ARE, Husband?
Is it?
I know it's hard. I'm also losing my sense of who I am at times, especially when I think about pursuing a relationship with another woman.
Please don't let your wife's actions turn you into something less than yourself.
If you want out of the marriage, then inititate divorce proceedings. My sense is you haven't really gotten your detachment and GAL activities into full swing. It's not time yet.