I have only finished Cake Island.
Well, seeing as you don't mind spoilers...
After wearing it a few times, the suit triggered his dormant Germa modifications (two times, I believe). He now has an exoskeleton similar to his brothers, so swords and bullets don't do anything to him anymore. However, just like his brothers, he is starting to lose his emotions, and he's panicking because he considers them "monsters" and doesn't want to be like them.
We're now at the point where he's trying to decide which version of himself is more valuable to Luffy: the womanizing human side that can't hit women? or the "Soldier of Science," which is cold and doesn't hesitate.