
Have his children, become a good mother, (show you possess the instinct to care for others) wait for 3 things to happen (hopefully not all at once): a family member of his to die, financial ruin, or a seemingly terminal illness to befall him. It is only in the face of great loss that men tend to “open up”.
Ok reading the other comments and realizing I missed a spot. Maybe obvious but this doesn’t apply to asking him things you’d be extremely likely to use against him in the future (trauma, insecurities & whatnot). He’ll probably lie to you about those as a precaution even if you haven’t personally earned it yet. If you HAVE, the ship may have sailed on that stuff and you’ll have to either apologize (AND IMPROVE(!!)) or otherwise just keep it light and inoffensive