I'm getting desperate because i cannot un-equip the summon familiar spell from my right hand, the only option is to put a spell of your choosing in the left hand but the right hand spell cannot be changed. Well i used to be able to change it i think, but now i simply cannot get around it. Is there a button to un-equip a spell?

go on the spell in the menu and click the right trigger

One related problem, so far I uses bow, sword and shield and the healing spell, assigned bow to 1, sword to 2 and heal to 3, heal goes in left hand. Switching between bow and sword is works nice, however heal removes shield and even assigning shield to 4 don't work.

Any tricks here?

Why i can't equip firebolt spell in both hands? I can equip it on left hand, but not on right. Can do it only with flames spell. I'm playing with High Elve.