1) I noticed that your enclosure seems very sparse. Paper towels and maybe 1 hide spot?
I always make my vivarium mimic their natural environment as much as possible. Mine is in a 60-gallon setup with sand, many hiding spots, climbing spots and digging area. He stopped musking within 2 weeks, has never hissed nor bitten.
2) When you handle, speak to it in low, reassuring tones. Convey to it with your mind and your touch that it is safe. While holding, SWAY from side to side. When their heads point down and you sway, it almost hypnotizes them.
2) Some snakes just DO NOT do well with captivity and being handled. Some can be extremely aggressive and non-typical of their species.
If your setup is improved, you handle often and all the snake's physical needs are being met, yet it continues to bite, you are better off swapping for a new model. The individual makes all the difference - just like in dating & marriage.