@karthmin is a guy INFP
I’m also currently writing two male INFP characters, one of them a very main character.
Keep in mind there are a lot of shades of INFP. Knowing enneagram types might help refine things a little.
Personally, I suspect that:
1. This really depends. INFPs are the ultimate take you by surprise type (imho). Even in dramatic situations, they can be very placid, or meek, or go berserk, or take control, or reason intensely, or try to calm things down. Largely, it depends on if their Core Values are at stake. They all have a little council chamber with themselves wherein they are battered by emotions and try to press forward carefully, walking a straight line, keeping to guiding principles or habits. (Oh, Kylo Ren is an INFP)
2. If he has learned not to cry, he may release his emotions in an unhealthy way on others.
3. Protectively, probably maintaining a certain mysterious distance. When relaxed, can be nerdy.
4. For the first part of this question, see my answer to point one. For the second part, he’d probably explode. 😛