Sylvester Archipelago

+10 to Constitution; +7 to Strength; free combat skill; four free combat skill points.

Can you only use this to take skills from the skill tree, or can you spend it on, say, a skill for wearing armor?
Also, I'm interested in whether the damage of "percentage" spells (like fireball) is based on the maximum or current health.
Does freezing multiply with critical hit?
Does Winter's Breath trigger with a counterattack?

Added after 10 minutes
Oh yes, does the two-handed weapon passive for blocking damage work without a weapon?