Trying to become Thane of Morthal. Hope I got the name right in the title. I have completed 2 of the 3 quests to help the people of Morthal. How di I get the third? I have tried reading my Skyrim Guide but I can't find the person I am looking for.

I speak to Lami and Benor but I get no quest or options to do anything for them. I think I read something about you will not get a quest untill you finish another quest. So my question now is, holding me back?

Here is my Misc quests I have active.

Investigate the Bards College.
Bring Ancient Falmer Tome to Urag-gro Shub
Find the copy of Chimarvamidium
Speak with Constance Michel about Adoption
Bring one Night Falls on Sentinel to Rustleif
Head to the Solitude Court
Assist the people of Hjaalmarch (2/3)
Find the source of power in Rannveig's Fast
Find Red Eagle's Sword
Joint the Imperial Legion
Joint the Stormcloack rebellion

So is one of these quests holding me back?

Rustleif's and Lami's quests are both "Rare gifts" radiant quests, so if you get the book for Rustlefi first, Lami should offer her quest.

Why Benor doesn't offer you a fight, I don't know, though. The key line is to answer him when he claims to be the best warrior in Morthal.

Which two other quests did you do? Did you deliver the letter for Idgrod (the Younger)? That's an easy one. Or deliver Gorm's letter to Captain Aldis in Solitude (if you have not completed the Civil War questline in favor of the Stormcloaks). You could also try selling firewood to Jorgen or ore to Pactur in Stonehills.