ladykyera999 I'm guessing you mean 1.5 GB memory, not 15, since the game can't use anywhere close to that much. But the real question is how quickly it increases, or if it's stable until you get a RAM spike for some unknown reason.
I would add NRaas Register to the list, not because you definitely need it but because I've seen enough errors over time that Register could resolve that it's worth keeping around. You don't need to do anything with it, just let it do its job. And if your sims ever travel, I would absolutely add Traveler as well. Among other things, it replaces the fragile EA travel transition with one that's much more stable. You don't need to configure Traveler either, although it and Register do both have user-accessible settings should you want to tweak them.
You may or may not get some benefit from Traffic as well. It is most helpful in Starlight Shores, where sims high in their Showtime professions get to use limos, but these limos never get deleted. I've seen cases where several thousand accumulate before Overwatch deletes them each night.
Again though, none of this has anything to do with Error 16. That's OneDrive-related most of the time. If you want to see your options for managing OneDrive, please read this guide, which was written with Sims 4 in mind but applies equally to Sims 3:
📓[GUIDE] [PC] Managing OneDrive | EA Forums - 12636625