You can read a good overview on hip dysplasia here
http://marvistavet.com/html/body_hip_dysplasia.html
which goes over treatment options.
The supplements are a good choice to help him but surgical repair may give him a long happy life with you.
Yes stairs can be hard on a dog with hip issues because going up them the dog carries most of its weight on the rear end.
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics