He is having some ups and downs. I would take any levels out and just have floor toys now. You can add some extra interest at floor level to make up for losing the levels - like extra tunnels and hidey places and hide some treats around the cage to distract him from the change.
Ears down suggests pain or discomfort. If your vet doesn't prescribe Metacam I would see a different vet. It is commonly prescribed for hamsters even though technically it's cat medicine. I know a vet I saw took quite a while to calculate the dose for hamster (which ended up being a drop or two) - she said although a hamster weighs a lot less, it doesn't just go on weight because hamsters have a faster metabolism and that has to be factored in as well.
Another vet I saw wouldn't prescribe Metacam for our last Syrian Charlie, because she thought he may have Cushings, and Metacam is contraindicated with Cushings - speeds it up apparently. That was tough because it wasn't certain it was Cushings.
It could be that your vet suspected Cushings (weakness of back legs and loss of hair in certain areas, and a bit of a pot belly are some symptoms, but they can also be the symptoms of old age).
See how he goes. If he does have Cushings, the steroid injection may have accelerated it. Steroids and Cushings don't go together. So that may be why he got a bit worse and had his ears down. Which suggests your vet hadn't considered Cushings. But sounds like he is recovering from that now.
It's difficult to know whether to get a second opinion or leave him, as vet visits are stressful. Most vets can't do a blood test to diagnose Cushings (unless you live in London I think), so taking him to the vets wouldn't help with a definite diagnosis. When Charlie couldn't have Metacam I did look at herbs to see if there was anything that could help with pain relief and found some that were hamster safe, but by that stage Charlie was less interested in food - and picky anyway
Willow Bark is one (it's where aspirin comes from) and it's safe for hamsters to chew - if they're interested in chewing it! I also bought a bag of small pieces of burdock root - which is supposed to help joint pain and be anti-inflammatory and also safe for hamsters. Charlie took that if I put it out but no idea whether he ate it or just hoarded it.
Baldwins herbalists online sell all those kind of things by the ounce.
Otherwise just see how he goes maybe and let him eat whatever he wants and lots of nice treats
Even a bit of cake wouldn't be such a bad thing as a one off. Rice krispies, cornflakes - scrambled egg, some chicken and pumpkin baby food - just anything that makes his life nice.