Nap/Nighttime Sleep and Feeding Troubles for our 16 month toddler - seriously struggling and not sure what to do - help?

The schedule is usually he wakes up about 6am, lunch at 11:30am and nap starting around 12/12:30 but in the past few days, he's been refusing to go to bed and not tired in the slightest (even though he looks visually tired). He's just wired. Today was a really bad day where he woke up at 5:45 and didn't fall asleep for his nap until 2:15.

The really annoying thing is that although we use milk as part of our bedtime routine with a food snack (but not feed to sleep with a bottle) he guzzles it throughout the night too. Right now, he's drank like 8-10oz of milk and at night, he will have about 16oz of milk between snack before bed and night wakings (he's currently waking up every 2.5-3 hours still). There is no way that this kid needs that much milk before a nap and before sleeping for the night. This is ridiculous. Our nephew was weaned off of nightfeeding at 4.5 months (doctor recommended for the purposes of sleep training) yet our toddler needs to guzzle like a full size SUV. We are trying to get him off bottles too because it's not recommended to give bottles as they get older for the health of their teeth. Right now he has a bedtime snack (food) with a straw cup of milk, but night wakings are still with a bottle.

Maybe we are giving him too much milk but he's sometimes not a great eater. It really depends on what we give him. The doctors advice was “well, just give him less at night and he’ll eat more during the day, simple!” Thanks Doc - Much easier said than done.

During the night, he wakes up and groans/grunts/screamy whines like he's trying to do the biggest shit of his life. Every night - it's always like that. The thing is a lot of the time, he has his eyes closed when he does it (can a infant/toddler have a nightmare every night? - doctor didn't really seem to care when we mentioned this). He hasn't woken up happy since month 3. Sometimes he will go back to sleep without milk, but others he will need milk and won’t settle without it. Or he needs to be held/carried and does not like being held with us sitting down.

For the record, he was sleeping through the night until about the 1 year old mark and it's been downhill since.

We're just really lost at this point...