To answer your last question/problem the Advanced Town Portal spell says in the description that it teleports you to the nearest friendly town with an Advanced Town Portal building.
Your Advanced Town Portal spell is probably grayed out because you are already in the town it would teleport you to, so casting it would do nothing. You can test this by taking a step away from your town and see if the spell is available again.
From your description it does sound like you should be able to use the Basic Town Portal spell to teleport to your other town. You should make sure that the other town does not have atwo hero in it. If another hero is occupying the space that the hero you are trying to move would teleport intoother town is completely occupied, you will not be able to cast the spell.
If the target spacetown is clearnot full and you have the right buildings and you still cannot cast the spell, it is probably a bug, so you should try saving and reloading to fix the problem.
As the others have said, you cannot use either Town Portal spell to teleport to the fort anyway because the spells only allow you to teleport to towns that have the corresponding buildings, and you cannot build those buildings in a fortforts are not towns.