I even saved the Dark Brotherhood and Bard's College for the next playthrough, and don't want to level skills I'm not using but it's so hard to stop!

Just try creating a new character for fun who is the polar opposite of your first character.

I had a lot of fun trying out a few different playing styles. A great deal of work must have gone into making each of Stealth, Magic, Sword&Shield, Archery, 2-handed, etc., so much fun to play.

Yeah that was my plan, but I'm still so engrossed with this character I can't stop!

If you want to continue with the same character without leveling other skills you can simply continue using the skills that you already leveled. You can continue indefinitely as a level 50 character which is also the cap for most enemies and this way have a more balanced game than someone who reaches level 80 and is good at just about everything.

I would look within all the Perk Trees you have not used up to this point just to make sure there aren't any more multipliers or bonuses you can get for your primary chosen skills. For instance, I run an archery first character and under the sneak tree found a archery bonus as one of the perks where arrows do what I believe to be 3X damage in sneak mode.

I know that's not the only example I have found up to this point. Then you can begin working on said tree to gain more bonuses to the skills you already use most that are maxed.

You may already know all of this but I just wanted to throw it out so you could look into it had you not known.

Also, I feel what you're saying about how addicting a character can be if you take the time to develop their story. I can't put my character down.

I just made a Bosmer I plan on being a mage, odd choice but elemental resistance isn't working since the patch but oh well.

Omg, what's the deal?