My wife has 4 other kids 3 are gangmembers one shot the other stabbed I have a 4 year old with do I have a chance to have full costody due to my son being unsafe around her other kids?

No ideal why this is titled abandonment, unless you have done it, Being a bad parent or kids getting into gangs is not abandonment. Having some older kids in the gangs, may in their local courts even been seen as just a sad result of the area and life they live.
Are you current in all child support, I ask since that will be their side, we could live better if he had only paid his support. They will try and shift blame.

Next there is no for sure, you will have to file a motion for custody and use proof of a bad home life as the reason,

This does appear to be a situation that could be seen as a danger to the child. But as Chuck said, we can't predict what a court will do.

And, in the future, please use a title for your question that pertains to the subject. I've edited the title as an example.