you are running a lot of script heavy mods (and even more just scripted mods). this sounds like it is very likely the cause. disabling a few at a time will not solve the problem. most of them will need to be disabled in order to notice, but as said this must be done on a new game.
plus, some of them quest mods have an aweful lot of reported bugs, which can mean: Freezes, Crashes, and simple mechanics not working. (which is why i mentioned before, always check the bugs tab, it gives you a very good idea in just how stable the mod actually is based on other people experiences)
it is never a good idea to run a lot of quest mods at the same time (also applies to running many mods that are script based).
so yea i am going to say the issue is literally down to a script heavy setup.
Beyond Skyrim Bruma
Moon and Star
Legacy of the Dragonborn
Wheels of Lull
that is just to many scripted mods to have running at the same time
i am very certain that, you are getting many crashes because the game just cannot handle that amount of scripts being fired constantly.
big quest mods are literally designed to be the only script intensive mods (completely standalone) you run, they should not be enabled with each other.
their is a limit to everything. you simply have exceeded it, thus causing the issues.
the only solution is to severely cut down on how many scripted mods you are using, and try to get used to the idea of creating new playthroughs each with very specific mods to enable. more specifically, have a new playthrough per heavily scripted mod.
so what you do, create new playthrough, only do the quest mod, fully complete it, delete the playthrough start another new playthrough with another quest mod, rinse and repeat, then if you like the quest mod that much, you keep it as a an ultimate playthrough which will be the playthrough you keep.
also ensure you have as few mods as possible when doing these quest only playthroughs
choose the mods you need, rather then the mods you want. basically meaning, only keep the mods you simply cannot live without, the less mods you have, the more successful you will end up being with a stable game. less mods = less problems = less stress on the game, and finally: this will make it much easier to resolve problems should they arise: understand that the game has its own limitations that is beyond your control, and likewise your hardware has limitations.
also as general feedback: really think about the mods you are looking at, only download them if you absolutely must have them.