You will have to test a lot. Rescale your output to something around 360p or 480p maybe and see if that helps. Lower the fps to 30 or even less.
Your cpu is actually not enough for a decent stream but you can try to get something running. As mentioned, you will have to test a lot, we unfortunately cannot give exact values that will work.
If you plan to play a game on the same PC while streaming I would really recommend to upgrade your hardware to at least an up to date i5 or i7 system.