Both carprofen and tramadol can cause kidney problems, so make sure you talk to your vet about starting them up again.
Sort of a side issue right now, considering the kidney management takes precedence, but how severe was the HD? It might be that the Dasuquin, Wellactin, and moderate exercise (esp. low impact exercise like swimming) will be enough to keep your boy limber. Weight is likely not an issue right now, but if you can keep him on the light side of normal, that will also be beneficial for his hips. With luck, maybe the HD can be managed from here on out without having to resort to the meds that might further impact his kidney function.