Hi guys,
I have a Sinaloan Milk Snake named Max. I have had him for about 3 or 4 years and according to the previous owner he is 16, he is about 4 feet long. Within the past year or so I've noticed that he's lost some weight and he sheds 1-2 times per month. I feed him 2 mice every other week, although recently I've had to cut down to one mouse because they are so expensive here and I have other snakes to feed

I keep him in a 20 gal aquarium with a screen top, in aspen bedding, a heat pad under left side of the tank and on the right is a big water bowl large enough for him to fit his whole body in. Temps are around 80-90 on hot side and 75-80 on the cool. Humidity is around 30-40%. He poops regularly, and his mouth is clean. No bubbles/signs of RI, although sometimes he dunks his head in the water bowl and comes out making hissing/coughing noises. (weird?)

So basically my questions are, is he healthy, am I doing everything right?
Is it normal for an older milk snake to be shedding so much??
Is it normal for an older snake to lose weight? (I can see a ridge along the top of his back, I'm assuming it is his spine.)
It has always been semi visible but I feel like now it's becoming more prominent.
Should I feed him more?
Also, when he sheds he often sheds in pieces and gets the caps stuck on his eyes. Just want to know what I can do to help him and if this stuff is typical of an older snake.
Thanks for reading.