About this frost troll issue, as i said earlier, this was my hardest fight. I managed to kill it by first shooting at it with an enchanted bow, then quickly climbing a rock, and shooting a few more arrows at it as it ran away, then going back on the road with a fire spell and a sword. Instead of emptying my mana bar at it, i used the fire spell every few seconds to keep it on fire, gulped down a couple health potions when he landed a hit, and otherwise just backpedaled and swung my sword at it, with an occasionnal shout in between to interrupt his attacks. It worked pretty well. There is also a troll hunting guide in the dragonsreach's mage quarters, which says basically that fire prevents trolls from regenerating (but only as long as you keep them under the effect, i guess), and that the longer the fight, the more the troll has an advantage.
Edit : now that i think about it, the "on fire" effect probably deals enough damage that you can only run away/dodge and use short bursts of fire spell to keep him burning. Maybe.
Edit 2: oh and while i'm at it, i noticed a message about unlocking the sky voice or something like that after reading all the 10 stone tablets on my way up the mountain, any idea what it does ? i couldn't find a menu referencing that, do i only need to go further down the main quest line or is it hidden deep in the menus ?