I'm letting you guys know I'm back to ck2 and finished some testing on the modlist. I didn't encounter the aforementioned bug with >75mb save. I also went way past the date of the save that couldn't be loaded, just to be safe. I had a similar bug midway the game, but I've noticed it happens only when you load the game through "continue". Loading the map first, allowed me to continue the game normally. I'm now conducting a full testing playthrough and will let you know if it confirms the tests.
On a side note: I tried to reduce the chance of Oedipus happening but it'd be too much of a hassle and the mod is not that important, so I turned it off for now. I'm also wondering if 'More Navigable Rivers' shouldn't be turned off as well, as it adds waaay too many small rivers on the map - basically (almost) every county has at least one, even in most of Africa. (ok, i've noticed that's vanilla HIP issue as well) That's way over the top imo and it affects balance, especially with 'Realistic Warfare'. But I'd like community opinion on this, so please, tell me what you think. If you have other mods you think should be out, tell me that as well.
EDIT: oh, I also encountered a bug with the smith not giving you created artifacts (there's a workaround for that) and 'Standalone sexual traits' showing all characters dicks after its event.