M.F.
Since he's such a heavy wetter, I would stop giving him milk right before bed. Since she stopped nursing at 11 months, I've given my daughter milk with dinner around 6:30 and nothing else before bed around 8. She started leaking at night around that age too, but she slept through it and the Pampers Extra Protection worked for us.
As for the sleep issues, often kids who fight naps are doing so because they are overtired. If he's waking at 5-5:30, what time is he napping? It's not uncommon for a 16 month old to still need 2 naps, especially if they are an early riser. Better sleep during the day also leads to better sleep at night. I would try laying your son down before he's showing signs of being tired, somewhere around 9 and again around 1, or right after an early lunch around 12 if you want to stick with only one nap.. Worst case scenario is that he cries in his crib and doesn't actually sleep, but you can teach him this is nap time and that means crib time. He might fuss, but if you set a time period that you want him to sleep (like 12-2) and don't go in there to comfort after you've tucked him in, he'll soon learn to sleep during that time instead of fussing and everyone will be better off. Good luck!