[Loredweller]

1) IIRC, there are barely enough quests for Thieves, so you should finish the staf quest (you could keep it anyway if you wished); also Gentleman Jim may have a pair of gauntlets for you and some quests to do with them of plain view (see if there is - what the word was, "bolmolagers" or something like it? - option in his talking list).
2) just so far to become independant with Cosades leave; don't worry about becoming Archblade;
3) i do not know about particular version, but Fortify Skill was removed from Mephala spell by some patch; it's still available via console, though;
4) consloe only, unless you get extensions - both Tribunal and Bloodmoon offers it for sale (though not at once, be warned);
5) SES from Suran and E of AldSotha there is Dwemer ruin, Mzahnch. E (or ESE) of it is smaller island, the Drunken Mudcrab Merchant is on it.
6) follow the advices of Percius Mercius (Steward of Ald'Ruhn FG); and he will be one who would promote you to this position - after all scores with Hard Heart would be set;
You may even skip Vivec FG quests - and for God's sake do not do last Hard-Hear's biddings (you'll see which ones). Do all you'd be offered in Ald'Ruhn and Sadrih Mora, though.