Hi, T.. Well, the good news is that children who are your son's age do not, DO NOT, ever starve themselves to death. If they are hungry, they will eat. So he must be getting enough food from somewhere.
The sippy cup at night does not mean he is hungry. It probably means he is thirsty. It also means that he likes having the comfort of milk from something he can suck on -- the sippy cup is sort of halfway like a bottle, so he likes it and uses it for taking care of thirst and for the pleasure of using it. He's being a big boy, but he's also getting the fun of sucking on what he's drinking. No harm in that at all. Let him drink it and be happy.
Please get out of the mindset of MAKING him eat dinner. Again, a 2-year-old WILL NOT starve himself. If daycare is feeding him every 2 hours, then he is eating quite a lot of food. If they are healthy snacks, as they should be, then he is doing fine.
The only time you need to worry about a toddler's eating habits is if they are (1) weird, like he wants to eat paint or dirt or other harmful things, or (2) he gets sick from what he eats, or (3) he throws up all the time, or (4) he's losing weight or not gaining steadily, a little bit at a time. Your son may not be in a growth spurt at this time, so he may not need to eat the way he ate before.
If you are concerned about getting him to eat at strictly scheduled times, then I think that, right there, is the problem, because his not an adult and will eat according to the needs of his body, not according to the clock. You can still have family time at the dinner table, but don't worry yourself sick over how much he eats. Keep the social thing going of the family sitting down together, because he needs that, and don't worry about anything else.
Also...DO NOT MAKE FOOD AN ISSUE FOR POWER STRUGGLES. You will only make yourself miserable in the long run, not to mention hurting your child. If your child knows he or she can upset you by not eating, then he will use that against you. The more upset you are about his eating habits, the more he will try to upset you. It's not because he is evil -- it's because at this stage in his life, he is on a long, exciting journey all about learning cause and effect. He is learning that doing certain things causes other things to happen, and this is absolutely fascinating for young children. This fascination continues into the rest of their childhood. So don't set yourself up for being his feeding experiment -- give meal times as little emotional impact as possible, except for making them wonderful family times.
When his body grows some more and he begins to need food on a schedule more like the one you and your partner keep, then he will conform to meal times. But don't expect to radically change the schedule he was on before and then have him respond exactly the same way.
Again, if he's eating every two hours all day long, HE'S EATING A LOT OF FOOD. Just make sure they are feeding him the right things. Make sure he isn't filling up on sugar, including the drinks they give him. And let him have all the milk he wants, as long as he's not allergic to it.
You're doing fine, Hon. Just relax and don't try to MAKE him eat. Your love for him isn't measured in how much you feed him, and his love for you isn't measured in how much he eats. Your love can't be measured, just observed. Enjoy him, and enjoy mealtimes.
Peace,
Syl