1 Don't you have dagger? Sneak behind it, stab it in the back (silver is the absolute best, I hear Daedric is good too). 2x, 3x or 4x damage depending on level.
2 Can you make a weakness to poison potion, anyone? Do that first and then poison the bag of bones.
3 Turn undead never worked for me, I just flame it until it dies (I'm mage).
1. See Kris' comments. (BTW, my char does not touch any weapon except a bow and does very well.)
2. No, you cannot make a wtp potion or poison. You can enchant or create spells with the effect however. The effect must be active on your target before you inflict them with poison. Weakness to poison, properly used, can temporarily bust poison immunity.
3. Turn undead works fine for me. Make sure that the magnitude of the spell is at least as great as the level of your foe, corrected for any possible armor-induced spell effectiveness penalty.