What you need to learn is effective killing techniques. Too many martial arts nowadays focus on competition style and mean nothing out in the streets when a guy pulls out a knife, or multiple opponents face you. I like pekiti tirsia, krav maga, any kali art, and muay thai. You will need some bjj though because ending up on the ground is inevitable. However, you dont need to be a black belt, a blue, or purple would take care of most opponents. I am a blue now and spar with any size opponents who are not bjj practitioners, some can be 300 lb, but it doesnt matter, it is all technique and moving fast.