Newly two year old tantrums

My husband has been deployed for six months and in that time a lot has changed for our two year old. We recently had a new baby and unfortunately despite my best efforts I think he feels replaced. He has started acting out in the worst ways if he doesn’t get what he wants I.e. hitting, biting, slapping and even hitting our newborn. I am trying everything to combat it in a calm and nurturing way but holy shit I can’t deal with it sometimes. I am really trying to not lose my temper but does anyone have any advice? I am practically a single parent and the only parent to discipline. I am lost, HELP?