Hi, I'm the anon with the game crashing. I should've given you more information; It is only one save that is crashing. I tried using a backup and an older save, but they all crash at 1:24 in the morning, and I have no idea why.
There could be a glitch in your game that is happening at the time for whatever reason.
Try using this cheat: resetsim *
That will reset all your sims in town, taking them all back to their homes, including any sims that are stuck or glitched. (Hopefully)
If you are still having issues after doing that and you followed all the help offered in our FAQ, I recommend you move the family into a new save.