Before restoring his sanity, did you go towards the front of Mardaneus' house and trigger the cut scene with him and Lanalor, where Lanilor gets frozen? Did you go through the well into Mardaneus' house and convince him to free Lanilor? The next time you enter the catacombs after that, Lanilor should bring you the other teleporter stone.
Seth gave (or will give) you a quest to arrange an escort for the healers. Leave Aleroth and follow the path, head east across the bridge and check your map for the location of the barracks. You can run around Aleroth killing orcs, but there are a couple quests you can get that (if completed before the escort quest) will move the healers without your help so you miss the experience points. Don't enter the troll cave by the bridge before getting a quest to deal with the trolls.
