So, Madanach needs to die, but the only thing I hace to kill him are some pickaxes or a shiv, and I have no one handed training. I'm level 18 and have no one handed skill. I'm locked in prison and can't kill this guy. Any tips to getting my weapons back so I can down this guy?

You can't get your weapons before. If you want to escape, pickpocket his key and escape. If you want to kill him, help him up until he gives you your stuff back and the unique armor. Before he leaves, equip your stuff and attack him. After you kill him, make sure to leave quickly as a guard will come for you and you will receive the unique ring from Thonar.

I've tried picking his pocket, he has no key.

I've tried pick pocketing him too and all he had was a note. Anyways, I just helped him escaped, if I gotta deal with him later then so be it. I was at level 37 with flawless Orcish heavy armor when I was in this jail and got my ass kicked when all those guys jumped me. I only tried to kill him once though and after I was killed I just figured to hell with it.

MAdanach doesnt have to die for the quest to be resolved.... and if you really want to kill him use a shiv...

He's an extremely powerful mage. The only way I was able to beat him is because I was a breton. Breton blood is the best racial passive and Dragonskin is the second best racial power (although it's actually more useful than Berserk against mages). If you're a breton, sneak attack him with dual weapons, then equip healing in one hand and an attack spell in the other. Trigger Dragonskin and hold down both spells. You'll be absorbing 50% of the spell attacks, taking no damage and pretty much always refilling magicka to full. This lets you keep constant damage and healing active, which should let you beat him.

If you're not a breton... well, have fun. Bretons are able to trivialize difficult mage battles once a day. Everyone else has to actually deal with those hard fights.

Well I finally got past him using dual pickaxes. Took literally 19 attempts, but I squeezed out.