Questions about health and multiple weapon.

If a warrior already lost some of his health, does equipping a negative health weapon lower his current health? Or does it simply lower his health maximum? Also, what happens when he equips a positive health weapon?

What happens when a defender(defense=2) equips a katana(-5) and a shield(+2)? Does his defense drop to 0 then to 2? or does it simply count the total (2-5+2=-1 < 0) and becomes 0?