Ohhhhhhhh @Duplofez I am getting red flags all over the place here.
You say he is good at conflict, at being calm etc in an argument...
Do those debates end up with him admitting he is wrong ever, or with you agreeing that he is right and you're wrong?
Is he actually good at dealing with conflict and disagreement, or is he in fact good at making you submit?
Because it seems odd he can't take constructive criticism and feedback that is less than glowingly positive at work... and yet can handle disagreement over opinions and can back down and admit he's wrong at home.
Those two things don't really go together.
I fear that his attempts to go self employed are going to mean YOU financially supporting HIM...over and over if it fails (And if he is no good at receiving and utilising constructive criticism, then it will fail...)
OR if it does take off (and I would generally expect a business to take two to three years to be properly profitable, depeneding on what it is of course)... Then he will be far too busy for you, he will prioritise work over everything else and blame you and any children you have together for that because 'I need to work this hard to pay for you and the children'...
And he will then be able to opt out of any of the boring, sticky, awkward, unpleasant bits of marriage and parenthood because 'sorry I have to work'...
I'd ask him about the business.
Ask to see his business plan.
Ask specifically 'at what point will this business stand on its own two feet, so that you can take a step back and let employees do the bulk of the work'..
Because that is generally the goal of being self employed vs employed by someone else (rather than just being self employed to earn money because its the only option you have).
If he tells you that there will NEVER be a time when the business can be left to trundle along with 9 to 5 input from him on weekdays, and he can take two, three week holidays from time to time... then get out, run!
It won't work and he will be a workaholic you never see and when you do, he'll be a grumpy arsehole.