So I am a CC junkie, and I have about 800 items installed give or take a few. My game runs fine (slow but fine.) But anytime I now try to install more, I go to press play or even launch without the launcher and there's a black screen (which is normal) but instead of waiting for a minute or two it imediently crashes. I have room on my PC but I don't know how to fix it.

It's not about the amount, but the quality of what you have installed. It seems you installed broken custom content OR it could be that you install a mod that doesn't match your patch level OR the mod requires something you don't have installed. For example, I remember than NRaas' Cupcake would crash your game IF you don't have the required Store set (bakery) installed.
I recommend that you remove ALL your CC and start the 50% method of installation.