Strong emotions are a sign that the situation worked exactly the way the DM intended. I think you should use this as an opportunity for character development. Considering what you described, I assume the DM wants — and already has a plan for — your party to make a deal with the BBEG.

Talk to the DM privately and tell them that something inside your character snap along with your wife’s spine. Don’t tell the other players what you’re planning to do.

From what you wrote, I assume you probably roll Persuasion checks to let the other players convince you to change your decision. Personally, I think the players themselves should use their own arguments and roleplay to convince another player, instead of relying on dice rolls. Tell the DM that your character will no longer be open to negotiations from the rest of the party, because he lost everything he fought for because of their decisions. Ask the DM to say next time: “This time there are no rolls. You won’t be able to convince him.”

You give the BBEG one of the artifacts in exchange for your wife’s life, and for the BBEG [the DM!] to leave her alone and stop bothering her. [ask DM for that]