I've added 2 quarts of Mopar ATF+4. All I have is 2 quarts. I'm only running this fluid until clutch 500 mile break in is complete and then I'm changing it for some more fresh and adding a magnetic drain plug.

Question is, is 2 quarts enough to run it with? Or should I pick up another one?

It takes a little over 2. You fill it until it runs out of the fill hole. You should be able to check and see how close it is with your finger. If it's right there at the edge you should be fine.