I remember making a kind of nest from pillows around my daughters - with space to still move around of course. They seemed to feel secure and made the bed not feel quite so big!!
Lots of familiar toys as well and I put bed guards both sides as well. Good luck!!
I used to read to mine every night, and then tuck them up, give them a kiss, and say "right - that's it for tonight" - and leave. We left night lights on in the rooms at first - then the landing light, so that they gradually got used to the dark, and we still don't shut their doors right to, so that they can hear that we're downstairs.
Spray some of your perfume on his pyjamas or let him sleep with an item of your clothing so he can smell you. It will comfort him. I did that and it worked a treat.
Depends what kind of bed it is, my boys moved from a cot to one of the little Ikea extendable beds with the bar across and they moved to it quite easily as it still felt quite small. The moved at about a year old though, because they were both climbers. They moved to a full size, midi bed with the tent underneath at about 2 and a half or 3 again with no problems - I think because that still has the bars round it. I found that putting a pillow about two thirds of the way down and filling the bottom bit with soft toys made it look a bit smaller.
Hope you get sorted out and have a better night tonight!