I had to get rid of all four Rising City mods, Unique NPCs / Monsters, and (I don't see it there but, sparingly use Awesome Follower Tweaks to make new followers). Most of those would cause memory related CTDs all by themselves, but after uninstalling them I no longer have save bloat problems.
If a save game CTDs on loading it, check if the save file is about >60 megs. Mine hover around 30~40. If you see a spike in size comparative to the list of saves then it's bloated (and sadly already has been borked for some time now).
Delete the bloated save files. When you finally do get an older save to load, immediately try to save the game. If that save is borked too, it will crash. You can keep deleting saves until you find one that will save, but in all likelihood (you'll lose about ten hours) as you approach the same amount of in-game time or trouble locations, it will crash or save-bloat again.
Uninstall at least those four mods and make a new game.
And if you want to play F4 heavily modified into reality, start with getting Darker Nights, and Interior Lighting Overhaul. You don't really need new locations to enjoy F4 again, just the same chance of falling off a cliff because you can't see anything, or dying from radiation because you haven't showered (Get Dirty), than you have of getting shot.
You'll also want a 'flashlight' mod that extends the light casting range of headlamps and PA (not the pipboy light). You'll just have to pretend that using it completely gives away your position, which it doesn't.
I have the maximum amount of plugins that you can have: 255. The 'divide them into two' isn't an option I'd enjoy trying. You don't just throw 255 mods at F4, you install a few at a time and play the game. If the game breaks, it's in one of the sets you just installed.
That's also more for CTD on game start up, not loading a save. And if you find a mod that you have to remove, it's time to start a new game. Additions mid game are ok, removal is not. Undoubtedly it's my load order that CTDs the game 9 out of 10 times every time I try to start the game exe, but once past that, it's smooth sailing until War of the Commonwealth spawns too many npcs.
"Suddenly without any change in the game or Nexus" : CTDs. That was a problem you created when you installed a mod and it's finally rearing its head (or you don't have it blocked in the firewall, or haven't told Steam to shove their updates back where they got them). If you don't have a save with twenty hours on it, having started with all the mods already in question, it's still an unverified-to-be-stable installation, and you shouldn't have moved on to installing the next set of mods.