Hi. It's great that you have a good sized wheel in there. But the cage is really small
I think we are all maybe pussyfooting a bit about cage size! They do need a fair bit of space to exercise, dig, burrow and climb onto levels and so on. I think it would be a good idea to have a bigger cage so he can explore and exercise more. As long as there are plenty of hidey places in a larger space I'm sure he would enjoy it.
Are you in the Uk or the US or elsewhere? The minimum recommended floorspace size in the US is 480 square inches which is about 70cm by 40cm - that's not huge but a fairly good size for a dwarf hammy and you can go much bigger than that - some people have a dwarf in a detolf hack which is over 5 foot long
In Germany they recommend a minimum size of 100cm by 50cm. One larger cage is better than smaller units joined together, so they can move around freely and have normal behaviours.
I think he'd really appreciate having more enrichment in a cage. That seems to be the key word these days. It includes depth of substrate, a nice dark house to build a nest in, tunnels and hidey places (there are lots of tutorials for making toys). A shelf in a cage gives them something to hide under and climb up onto with extra things to do.
There is a really good selection of cages in the Uk. They are pretty expensive in the US and not a huge choice so most people there use glass tanks or make bin cages.
It's hard to imagine sometimes - and to get perspectives - here are some examples of dwarf hamster bin cages and some useful info about hammy cages
https://hammyhappenings.wordpress.co...cage-bin-cage/
This is our syrian's 100cm cage. He's a big syrian, so it has big stuff in it lol - but some people use this cage for a dwarf hamster as well.
Erin from Erin's Hamsters had a detolf for her dwarf hammy - she did a review of it here. It's pretty big. But you can also set up a smaller 30 gallon tank or 80cm cage in a similar way. It's a cheap option for a large glass tank as it costs about £40. I would love one but don't have the space.
https://www.youtube.com/watch?v=SQXI8pgRhmA