Does he masturbate at all? Allowing and encouraging physical relief would help normalize him. The other thing I would do is allow him to establish and defend a nest area. That way he would defend the nest, focus on it and work through his hormonal instincts. Right now all you are doing is fighting nature and thousands of years of evolution. Instead of frustrating him, accommodate his instincts.
I had the same problem with Harley PFLB. He did not normalize his behavior until I gave him a nest box on his cage and allowed him to build a nest inside. Once he did that, he started coming back to me for attention and scritching, after which he would masturbate, go into his nest and rearrange everything. By allowing him to express his instinct, he normalized himself.
He even courted the single hen tiels, actually getting Gracie Tiel as a companion. They groomed one another, perched side by side, but Gracie refused to allow him to mate with her. For four years he tended his nest, companioned Gracie a got scritching from me. Then 16 y/ o Gracie died. Harley was devastated. This was the fourth mate he had who died. So I got him a lovie mate and he and Blu do everything except actual mating. Harley comes to me for scritching, then masturbates on his perch. He's a happy bird now.
Stop fighting instincts. Feed them instead. The only purpose of a living creature is to produce more living creatures. Please don't go the hormone injection route and scramble his brain and instincts. Try doing what comes naturally instead. Please.