Don't tell him that if this is what he wants you're not going to stand in his way! You are not giving up. Do stay calm and tell him what you think and follow it up with understanding of where he's coming from. It is scarey! The only thing we have control over right now is ourselves. Maintain it! We have no power over our spouses or how they feel. We can only validate how they feel, and also let them know how we feel. God bless you and your marriage.
"Always go straight forward, and if you meet the devil, cut him in two and go between the pieces." - William Sturgis, clipper ship captain, 1830's.