So I've had no problem with my sims game until a few months ago. I had a ton of bad CC so I reinstalled. I redownloaded a lot of CC. I just got back into wanting to play the game this week.
Most of my files are .simpacks, only like 3 exchange sims, I have maybe 200 packages, which is nothing compared to what I've had in the past. The game runs simpacks perfectly fine, no problem at all, no lag, no anything. But when I try to add package files into the mix, I just get a black screen after launching.
If I play with just simpacks the game runs fine, if I play with package files, it runs, but is EXTREMELY laggy. If I run with both, I get a black screen that won't respond and I have to shut it off.
I've never had this problem before, I've tried reinstalling the game several times, deleting caches, deleting downloadedsims.index. I've looked up multiple forums and videos looking for a fix, but everything I do doesn't seem to work.

Have you checked your packages with the Dashboard tool? It's not 100% accurate but can point out bad cc or conflicts, etc. http://modthesims.info/d/387006

Did you check out the Game Problem help list from the sticky post: http://www.modthesims.info/wiki.php..._3_Game_Problem

I'm not entirely sure that it's the same problem, but try the steps in Game Help:Package File Lag^wiki to eliminate corrupted or Sims 2 package files as the cause.

I can't even get Dashboard working, I've tried several times, and it just crashes every time I try to use it.

Did you what Nysha suggested? Also did you check the requirements for the Dashboard to run from the download page?