I had first spent a bit killing off guards in all of the cities around Skyrim.

I have absolutely no idea what happened, but this is day 4, real days by the way, not in game, of things not re-spawning WHATSOEVER after I did this.

Each real day that has passed I try waiting about 90 in game days to see if anything changes, and nothing does. Items in dungeons, chests, and so on are properly respawning, but all my cities have no guards, and outside of picking up a quest to kill bandits, nothing will spawn in dungeons or camps, etc. Any help would be appreciated because I really hate having to revert ( I save so much I have absolutely no idea where to begin reloading ) or start new games.

Any help would be appreciated.

I wasn't aware that npc's respawn at all.

If they weren't supposed to be spawning, then it's taken a month for the game to figure this out
Everything HAD been respawning every two in game weeks or so.
Giants, Trolls, Bandits, Dremora, etc.
Now nothing respawns at all that I can find and it didn't start until I wiped out every guard I could find.