Thank you both! The moment I got Jmcrook's reply, I started prepping to give him a bath. I was able to rub all of his shed off with a damp towel after he soaked for a while.
Thankfully, he took care of his tail tip and eye caps himself, so I just had to get his back. He's all good to go now! (:
(The mites were taken care of by the end of January. Would they actually still have an effect on shedding weeks later??)
Snakes have slow metabolisms - certainly compared to humans. It takes them a while to show symptoms of disease - even mites - and a while to get back on track. Yes, he could still be stressed and/or dehydrated.