I think theory can convolute something that is simply a straight line.

I would not call sending a client a video a dual relationship, I'd call it a boundary crossing. I understand he could be sanctioned for it. Likewise, his manhood and sexuality have no relevance to you or your treatment.

There are several books on sexual abuse in therapy:
Surviving Therapist Abuse Bookstore - Therapy, Therapist Abuse and Professional Misconduct

You can email them TELL. I'm sure they'd have opinions.
TELL: Therapy Exploitation Link Line

It sounds like a gray situation because you've had a long relationship. You recently wrote about his "fantasies" and effusive flattery. Are you in a position simply to tell him to "knock it off" like a peer might do in a sexual harassment case? If you can't talk like peers, then I hope you find some assistance, because I believe most therapists would view this is very wrong. (I know it's tougher when 1) you're inside it 2) the relationship is colored so much by analysis.)

I assume he's a little young for the disinhibition that comes with the onset of senility, but that might be a possibility. I've seen dignified men turn to dirty-talking adolescents when they get older.