Hip Arthritis. Euthanasia?

Hi Myself and my boyfriend have a complicated problem with no good answer. Our 9 year old German Shepherd Havoc (who we love like a son) rear hips are completely shot. We have spent thousands on stem cell, acupuncture, adaquan injections etc etc. Everything but hip replacements which we can't afford (and might even be to late to do). Two months ago he was put on 10mg twice a day of prednisone as a last resort. Along with tramadol (up to 3 50mg 3 times a day). He really can't walk at all now. He stumbles and falls over. We have to help him get around so he doesn't hurt himself. Among other side effects like hunger, thirst, insomia, panting. He has now recently developed bloody stools from the prednisone. We rushed him into our vet. From how much of a downgrade in his ability to walk since our last visit. Our vet was worried about a spinal tumor or prostate cancer. Havoc was negative on both after x rays. Havoc also has as of this trip a right front leg elbow which is puffy and seemed larger then the other elbows bone. X rays on that confirmed it's arthritic. Our vet put Havoc on metacam (with the tramadol). Our vet has told us in a real short time Havoc wont have any use of his rear legs. We are considering putting Havoc down based on the pain he has from the hips. We have had experience with a Degenerative Mylopathy German Shepherd. He lived over a year and a half not being able to walk at all. We can handle a pet with a disability and no pain like with DM. One who can't walk and is in constant pain we can't. Our question is is it possible to give us a rough idea what the pain from our dogs hips would be. We are seeking as many opinions as possible. We realize you can't comment 100% on our specific dog as he isn't your patient. But a dog in general with these problems. How much pain would he in?? A plus is no side effects from the pred. But the pain is the worry. Thank You