1. No 2. Yes, enchants are specific to item slot, not type. For example: +xx damage can be on jewelry and gloves. 3. I have seen only one, and i can't really imagine possibility to have 2, unless on some unique/legendary/artifact items, but i doubt it. Enchants you have seen on the shield is one enchant giving 2 bonuses. 4. Enchants are not to diverse. There are hp/stam/magica ofc, resists, elemental damage, sneak(sneak radius+sneak cost), blocking(block cost + mitigation), defensive roll cost, sprint(reduced cost and increased speed), phys damage(mentioned above), combat stamina(health, magika) regeneration(flat numbers around 10 at lvl 50). Also there are some proc weapon enchants, i can remember only the one that has chance to boost your power. But set bonuses are really diverse and will be core part of any build.