My only observation regarding the advice on changing bedding is - I wouldn't make any sudden changes if he seems comfortable and is managing as he is. Clean outs and removing their familiar scent can be very stressful for them. And they are very fussy about their nest.
What is usually recommended here is, if they have difficulty walking about then just a thinner layer of substrate that is well pressed down. But I wouldn't remove the nest. How much substrate does he have now and what type?
Maybe you could add fleece in one half of the cage furthest away from his nest, instead of the substrate and see how he takes to it.
Because one thing that makes hamsters happy, even when old and doddery - is being able to have normal behaviours and they love messing about with bits of bedding and taking the odd bit to their nest.
Our last Syrian lived to 2 years and 8 months and still liked to use his wheel for a few seconds each day right up to two weeks before he died - even though he was quite distended and waddled when walking. And even up to a couple of days before he would still grab the odd bit of bedding on his way into his house to take for his nest - just habit.
I think of it like old people. They are happier left in their own homes with their own things around them - as long as it is safe.
So as long as there are no levels he can climb onto and fall from then I would just press down and compact his current substrate and just have it an inch deep maybe and leave his nest as it is.
But you can maybe go with your instincts on this as you know him. Fleece can also be chewed by hamsters and cause blockages and just because he 's old doesn't mean he might not decide it would be good to chew some nice soft fleece off to put in his nest!
So would suggest - thinking before making too many changes.
Rule of thumb is - remove any levels - maybe hang a hammock above then so they don't feel exposed with the levels removed. But high enough he can't climb up there into it and fall. To avoid him climbing and falling.
And have everything all at ground level but still with some interesting toys and tunnels for stimulation. Changing things, moving things, and cleaning out can really stress them. So if he can walk around the floor of the cage ok as it is I would hang fire on using fleece. He may like things just as they are