This is my second 100+ hour playthrough that I'm now basically forced to give up on. I can't go an hour without the game randomly crashing. It doesn't even have to be on a loading screen, which appears to be the most frequent kind of crash in this game, it'll often just lock up as I'm walking around (also it's worth mentioning that the game's performance is also horrendous at times, now. The buttons become unresponsive, especially run, and the audio can quite often become delayed. The framerate in some sections can drop to less than 1 frame per second).

On top of this, I have approximately 10 broken quests (again) and it's just not acceptable.

I've wasted a ridiculous amount of life on this game, it seems.

If you want to spend a bit more time on those characters you could try turning off all the autosave options and manually saving. That will decrease the amount of crashing.

The crashing happens without autosave as well.

The other character crashes as soon as you go near a city/village, regardless of autosave.

Have you been keeping up with the patches?

Yes, if anything the patches have actually caused performance to deteriorate.

Only the 1.6 patch should have caused more crashes and a few other problems, but turning off all autosave options should have got around the crashing. Is your Xbox 360 overheating perhaps?

Nope, it's nothing to do with the X360 and everything to do with Skyrim.