Question number 1! Where is Potters field set aside or territory?
Read the card - it's set-aside.
Question number 9! Can you use Image of J. on a fort in set aside?
By default, you can only target cards in play, so no. This makes questions 2 and 10 a moot point.
Question number 3! If Gates of Hell is used during a battle and I discard a hero from my deck and Davids Harp is up can I save a hero from my deck instead of one in battle?
David's Harp doesn't specify that you have to save the hero in battle, so that sounds legal to me.
Question number 4! What happens if a Magician is set aside with Magic Charms played on him? Is the artifact still active and can it be don'd?
Unless Magic Charms says it remains active in set-aside area, I would think the answer is no. DoN specifies an artifact in play (and that would be the default anyway), so the second answer is also no.
Question number 5! If I used Protection of Angels (the apostles fort protector thingy) on Gates o Hell could I place all the orange demons I discard from my deck into battle?
I think the discard is a cost you have to pay to do something, so no.
Question number 7! This is a dumb question but Tart. is set aside when played?
Yes.
Question number 8! Where is High Places? Territory or Set Aside?
It doesn't say it's set-aside, so it's in play.