Hi there. Please don't put vitamin drops in his water. It will be why he isn't drinking it. They're not necessary as they can get all the vitamins they need from a hamster mix and veg. It will put him off drinking the water. For now you could try putting a little dish of water in his cage to encourage him to drink (psychologically it's not the same as the bottle as he may be suspicious of the water bottle now). I'd suggest using a different bottle in a week or so instead of the dish (hamsters have a very strong sense of smell and he may just reject that bottle now even if it's cleaned out).
Best to put a dish of water on a shelf if possible as it can get contaminated or full of litter if it's sat on the litter. Also a very shallow dish so he can't fall in and get soaked or drown. A saucer would do but might be a bit big. Or the cleaned up lid off a jar maybe.
The Hamster Heaven is a good cage - a good size and very nice and the big front door is good for interacting with your hamster. However most of the contents are pretty useless really! It is better used with the external tubes removed and capped off and without the penthouse, so it's just a basic cage - otherwise they tend to develop abnormal behaviours such as nesting in the tubes or blocking the tubes up and peeing in them or the penthouse.
Personally I would remove everything except the solid plastic shelf and it's ladder and block off the tubes and leave the little plastic houses out (if they nest in those it gets very messy as they're not big enough).
This will also leave space for a Syrian sized wheel and a good house, then just add any toys you have. Something like a shoe box makes a good house - cut the bottom out and a hole for a door - it's big enough for them to feel secure and build a big nest - they need somewhere dark inside to retreat to.
Also put plenty of substrate/litter in the cage - at least 3 to 4" - best if a house is open underneath and sat on top of the litter so he can do normal behaviours like burying hoards under his nest.
Sounds like he needs some time to get fully tame with you - that's just time and patience. Bathtub taming is often a good idea (dry bathtub) - will post about that later but have to go now).
As regards moving him to another cage. You need to make it as stress-free a transition as possible - so fill new cage with new litter/substrate (it's bigger) and then spread the substrate from his old cage on top so it smells familiar. Don't clean anything - it'll be fine for another couple of weeks. Try and have things in a similar layout/location if possible. Adding something new is fine and interesting when you set up the new cage but keep some of his old toys and chews that smell familiar.
Cardboard or natural tubes and tunnels as floor toys tend to be better than the plastic ones and rat sized toys are best for Syrians really. Some syrians can actually get stuck in the "hamster sized" tubes.
I am sure he will love the Hamster Heaven. He'll need a good two weeks to settle in to a new cage though, so during that time don't move things around and change them - best to get it all set up first and then leave everything. Also don't do any cleanouts during that two weeks. Just spot clean the pee area a bit after a week maybe if it gets whiffy. I think the hamster heaven comes with a litter tray so use that and the cage should stay mostly clean anyway. Try putting it in a corner of the cage when you set it up but if your hamster chooses a different corner as a toilet you'll need to move the litter tray to that corner or he won't use it
Chinchilla bathing sand is good to put in a litter tray - soaks up the pee.
Nesting material - best is plain white toilet paper torn into strips. Don't use any fluffy bedding if you've been sold it - it's dangerous. A big pile of the paper strips somewhere in the cage. He will pouch some and busy himself building a nest with it in the house.
With the shoe box house, the lid can be a lift-off roof so you can check inside without needing to remove the house.
Cleanouts - big cage cleans are stressful for hamsters - it removes all their scent and they feel lost and invaded. Partial cleans are better. So spot clean or use the litter tray mostly and then you won't need to do a substrate clean for a few weeks or longer. And clean any other items a different week to doing the substrate - eg wheel one week, toys as and when- that way something always smells familiar to them so it's less stressful.