Ok first off, rest easy. Nursing overnight doesn't cause tooth decay. http://kellymom.com/ages/older-infant/tooth-decay/
if I nightweaned my DD when she got teeth, she would have been done at four months.
Second until baby's first birthday, it is perfectly fine if he doesn't eat a lot of solids. They are mostly for experimentation and learning. Some babies take longer to develop a mature digestive system able to cope with solids - particularly those with food sensitivities - and can rely mostly on breastmilk until well after 12 months without any issues.
If you are feeling dehydrated by morning, could you keep a water bottle by the bedside and have a quick drink while he nurses?
If he doesn't like bottles, you can just use a sippy cup or even an open cup to provide expressed milk while you are away.
Unless you are looking to do mother lead weaning, it is not generally recommended to night wean until 18 months of age. I know, it's a long time. If you did nightwean him then it might be much harder to get him back to sleep after he pees anyways. My 16 month old still nurses 2 to 4 times a night. She wakes, pees, then a few minutes of nursing and she's down. I don't know how I'd get any sleep if she didn't nurse down. If you're going to work the night shift, do you have a plan for how he will go to sleep without you after the potty at night? My DD pitched the pacifier at 12 months and I can't leave the house at night at all. All the singing, rocking, water in a sippy, etc with daddy doesn't work. It's boob or bust around here. I'm not trying to discourage you, just sharing my experience. Working with a baby is hard enough, I can't imagine doing the night shift. Good luck to you, I hope you find a system that works.