Even more questions. Thanks for bearing with me

1. Do potions stack? If I have a draught of fire resistance 30%, an elixir of fire resist 40% and my own creation of 17% fire resist, does this give me 87% resistance?

2. My character cannot smith enchanted gear, nor does she want to. Who can she pay to do it for her?

3. My character had done three [censored] favors for Sergius at the College, but he refuses to enchant anything for me. Will he ever offer this option? And why do I have the opportunity to ask about it if I cannot do it?

4. NPCs come up to me all the time, and ask me if I need anything. But I cannot talk to any of them. Why?

5. I can only find Illusion scrolls, which max at level 12. I assume, that as my mage increases her illusion perks, that these scrolls will actually be worth something? More importantly, does having higher level Illusion perks, help with illusion weapons?
For example: My character is level 22. She keeps finding staffs of Illusion that only go up to level 8, level 12, level 6. Will these staffs be effective with the right perks, or are they worthless? She finds staffs of destruction, which seem right to her level, btw.

6. Does Oakflesh and Stoneflesh stack?

7. Why do my arrows bounce off mudcrabs but can penetrate steel armor?

8. This guy came up to my character on the road. He looked around, lowered his voice and sold me skooma and moon sugar. AWWWW YEAH! But nothing happened. I know about Moon sugar in cooking... can I do something with skooma?

9. I hear talk, on the loading screens, of Detect LIfe and Detect Dead. Where can I get these? Where can I buy a Dispel spell? I desperately need one.

10. Wearing fur armor, vampire boots, apprentice hood, forsworn gauntlets, and an archer. This kind of serious light gear going to be okay as she moves up in levels? She would smith this kind of light gear as she could.

Phew... Thanks.