My main skills such as stealth and archery are maxed, light armor is getting close. But if I try to level skills like one-handed I get destroyed... Any tips?

Well. some easy ones to level are lockpicking, pickpocketing, blacksmithing and enchanting. Combat skills you've neglected will take more work, obviously. Best ones to mess with in that case would be blocking and 1-handed, as at least you'll be a little more survivable with a shield, while your whacking stuff with a sword or whatever. Just don't take on any real tough varmints until you skill them up a ways. Find some skeevers and mudcrabs and wolves to harrass

By level 42 I'm assuming your filthy rich by now, so just pay for training.

Limited to only 5 trains per level, it takes a long time to get a skill up that way. Let alone two or more skills. And you have to get more level ups, to be able to buy more skills. At 42, buying 5 trains in a lowbie skill doesn't move the next-level bar very far. Sure, he should definitely spend gold on those trains whenever he levels up, but he's still got a lot of hackin' and whackin' in his future to get anywhere.

level up your illusion magic to 50 and cast paralyze on someone then hit them as fast as you can with a cheap dagger until they get back up and then paralyze them again. You can get your illusion up to 50 by just repeatively casting one of the newest spells you are able to untill you get paralyze.

You can raise conjuration and destruction by summoning atronachs and then attacking them, if you get a frost atronach and hit it with firebolts, fireballs, or whatever the most recently aquired fire attack spell you got is it will level fairly quickly. If you dont want to fight the atronach hit it once, then wait 3 seconds before you hit it again, if you hit it too quickly in rapid succession it will turn hostile.

I have mastered every skill in the game except for pickpocket and alchemy without mods or cheats, It is a challange to switch from one branch to the other because you are effectively fighting level 50 bandits with a level 12 sword if you start on magic, and if you start with a sword you are casting pathetic little fire sparks at monsterious dragons.

My strategy for training lower skills is pay for training in desired skill, pickpocket money back, maybe raise some other skills while waiting to level if you haven't already, and then repeat. Goes much faster this way.

Paralyze is in the Alteration skill tree.

Training is your friend here. Sure, you can only train five times per level, but each session gives you quite a lead on the next level up. If/when the training doesn't knock you up a level, go grind some other skills for a little while and then you can train again.

Yes, I agree, that works quite well at lower levels. When over 42, however, like the OP, you're not going to get nearly as much mileage out of buying the lowbie skills- so you'll have a lot of work to do until your next levelup. Although if he hasn't done anything with pickpocket yet, a couple of hours of dinking around in a town or two can get that skill from 20 to 75, in a hurry. But that's one of the few quick 'n cheesy skills to level up easily. And quite profitable, too!