Destruction - Lightning spells
Heavy Armor(?) - ?
Invest in Health, Magicka, Health, Stamina(etc.)

Should I use a Two-Handed Warhammer, or a One-Handed Mace?

I'd say Hide armor because it looks like something he would use. As he would use a one-handed warhammer, but the game doesn't have one-handed ones, I'd say go for the 2 handed.

Destruction (invest your perks into the shock side of the tree)

Two-Handed (Focus on investing into hammer related perks)

Heavy-Armor (No helmets, only wear circlets.)

Smithing

Block (No shields)

Enchanting (Shock Enchants on weapons only, do what ever you want with your armor)