My main concern would be his not eating much - are you feeding him what he was eating at the breeders etc? Mine arrived with me at 14 weeks and usually meowed only when they were demanding food, but they had each other for company. If he is eating wet food though it may be that he simply doesn't like the dry food - one of mine wouldn't touch it until I eventually found a dry he liked - I was feeding him the dry he had at the breeders but he simply wasn't interested.
Also, having toys all over the floor is all very well but you need to play with him a lot to help bond with him and wear out that kitten energy - toys lying inert on the floor quite possibly don't interest him! Do you have a flying frenzy? They are a Bengal must have.
Have you booked a trip to the vet yet to get him checked out as already suggested? I actually don't think my two were much bigger than how he looks when they arrived with us, but if you are worried about the amount he is eating you really need to get him sorted on that front as soon as possible. Is he losing weight?
Three days really is nothing though and it sounds like he is missing his mother and siblings if he cries the second you leave him on his own. However, at four years old, my two are still incredibly noisy and vocal - so you need to get used to it - mine seem to only stop lately if they are eating
Jagger even goes out in the garden talking to himself at full volume