OUCH. The ground glass in my hands, wrists, hips, spine, and knees just flared up in sympathy.
I'm sorry to hear about this. Your hubby IS really young to be needing a THR, but on the other hand, he would probably do extremely well because of his youth. Just think---an operation, some physical therapy, and a lot of pain at first, but then it would be over and he could go on and live his life WITHOUT pain.
Of course, I say this knowing that I myself am holding off on a total knee replacement that I probably should've had five years ago. I'm considerably older than your spouse, but I'm holding off for pretty much the same reasons. So far, I've been able to manage with plain old ASA, two tabs PO BID. I worry about developing a GI bleed, but Tylenol was useless, Motrin, Aleve etc. didn't do much either, and I refuse to take Vicodin or other narcotics. So, I swallow my aspirin tablets and hope for the best.
Weight loss and warm-water exercise will certainly benefit your DH, but the joint damage has already been done, and he's going to need that surgery.......sooner rather than later, I should think.
Good luck to both of you as you make this decision!