2) The entire walkthrough focuses on breaking through the outpost. If you don't want it to be possible to take it so quickly, add a couple of hundred more Inquisitors, and I doubt I'll be able to break through it (except with Dark Magic).
3) Yes, level 34 should be fine. You can also throw in a few Ancient Silvan artifacts.
4) Regarding the landscape, there are entire areas that are simply filled with trees. For example, I try to place a bush or plant a mushroom between them. But I specialize in [M]aps, 136x136, where large forests are not needed. Here, I think, lag might occur. So, it's better not to.
5) Well, if you're going to reinforce the outpost, then yes, the Obelisks will become worthwhile.
6) I made a mistake; I meant caster. In the sense that they cast a lot of useful mass spells, frequently, and don't spend a lot of mana doing so.
7) Spell Luck? Sure, it's possible. It probably just didn't drop. On the other hand, it seems to affect spell power, and I didn't even take Chaos at the beginning