The save files that cause the crashing, I have no idea what is considered "normal" for the size of a save file, so you might have something there, but I've already turned off and unsubscribed from all of my mods, and I didn't have a mod manager or anything to keep track of them, so I can't really give you a comprehensive list of all the mods I had.
I had around 25, if that's any help.
Oh dear. I had some very similar issues when I realized just how *bad* the Workshop is for modding and wanted to migrate to the NMM or get rid of my Workshop mods altogether. Without a comprehensive list of all the mods you had installed, it is downright impossible to fully troubleshoot.
The two most likely candidates for what has caused this issue are either rogue scripts or save corruption. Often times if you just stop using a mod, it can make things worse (this was the case with some of the workshop mods I had, which was a pain to fix - took me the better part of a week to find the correct version of the mod I had installed before it would work again, and if it wasn't the Steam version, it wouldn't allow me to fix it - quite a pain).
With that said: When you removed the mods, did you make sure to read all the directions and ensure it was as simple as just turning them off? Item mods aren't so bad, but when you get into things that alter your character or whatnot, that's where things get interesting.
Additionally: It doesn't sound as though save bloat is your issue, which is good - that is a real pain to fix (previous issue I mentioned saw my files in excess of 100mb... truly ridiculous). So at least you don't have that problem.
Thankfully, there's still some hope for you. You can still go back to Steam and see which mods you have downloaded/installed recently, which means you can also go back and look in the descriptions to make sure you've uninstalled them correctly. If it is a matter of a mod incorrectly uninstalled, then that is a (comparitively) easy fix. Otherwise, it sounds a lot more like you may be facing corrupted saves, which I have also experienced... and there is absolutely nothing you can do in that case other than revert to a previous save and reload.
With all that said, I really miss some of the tools the old NVMM I used had - used to let me manage my characters, and also let me know what mods happened to be installed on a particular save (and the order they were installed in!). Invaluable for times like this when you get rid of all your mods and go "whoops, now what?"
Anyways, best of luck, sounds to me like you have some homework to do.