Yeah that rat seems huge for that snake. They should be as round/fat as the thickest part of your snake, give or take.
Also, have you tried the bag trick? (Put rat in a plastic bag and spin it around for like 30-60 seconds to make it dizzy then drop it in.) I have done this when feeding my 2 new snakes with no issue, and read at least somewhat that it helps more than hurts lol.