How frustrating to have no answers in all this time! Your doctor's response just confirms what I keep saying about some Ortho surgeons - they feel their job is finished when they confirm that the implant has healed, is not loose, and is not infected. That can leave us hanging - wondering what to do next. I had the same experience after hip replacements 15 years ago, the surgeon had me convinced that what I had was "Normal" so I tolerated the pain for almost 5 years. Then I learned he was wrong...

The pain and tenderness could have a couple of explanations. If I had this issue today, as a much wiser and more assertive patient, I would do the following -
First, find out exactly what hip implant I have - Manufacturer, Model, and materials. There is a registry, so the surgeon can provide this info. It is your right to insist on it.
Second, if ANY of the contact surfaces of the implant are chromium or cobalt I would ask for metals testing to see if it is shedding into my body. Either your surgeon or primary can order this.
Third, I would research the implant on-line to see if it has been a problem for others. Ignore all the law firm ads and look for other entries about it.
Fourth, I would see a neurologist to see if there is a nerve impingement causing your pain. Also have your spine checked carefully, as back issues can manifest in the hip, and vise versa.
Finally, if all of these are "negative", meaning the implant is safe and sound, and there are no discernable nerve issues, get a referral for a evaluation and PT with a rehabilitation clinic - think, a place that handles complex rehab, not just post-surgery stretches and exercises. After 3 years, you seem to have a great deal of deconditioning (eg can't raise leg, slouch) that needs to be addressed.

Please don't give up and "just live with it" without exhausting every avenue. Do you have a sympathetic primary you can connect with?
Sue