In my opinion, your reason for not wanting to do individual therapy first and separately is a little controlling. I know it's out of anxiety. Seeing how your partner acts on their own accord and not because you're forcing them to do something is very important information. If he does stop going to individual therapy, it's not your role to force him to start again. It's your role to assess what that means about the relationship and maybe even how much respect he's willing to give you and your wishes