Wow, Baron. If I were in Raspberry Surprise's shoes, I'd be crushed by your post. But if you guys have been married this long and in therapy, then probably nothing you've said is new to her. I give you credit for knowing yourself well enough to throw it all out there.
You two seem to love each other but have some fundamental incompatibilities. I guess the question becomes, do you stay together and work around them or give up and seek happiness on your own?
As a woman who spent many years with an unhappy husband, I can tell you that there is a certain amount of mistrust and resentment that develops. That is some tough shit to work through. Without even being conscious of it, I began seeing my husband as a self-pitying, self-righteous, martyring brat - which, of course, kills sexual desire and feeds the non-intimacy cycle. Even now, when we have a pretty fulfilling sex life, and he has other sexual and emotional outlets, I still have a strong negative emotional reaction if he's in a place where I perceive he wants something and I can't give it at the time. I think, "Oh no, here we go again. If I don't manage to put on the whore in the next three hours, I'll be emotionally battered."
I can't relate to your particular SM desires, but I feel confident saying that bringing someone else into your relationship, while relieving some stress, will create it's own unique ones. Please don't think, for even a second, that friendship necessarily alleviates time constraints. You will simply be replacing some old challenges with new ones.
It may work for you both. I would suggest, however, that if you choose to stay together, that while you're looking for your own fix, your wife be allowed the same freedom. You are seeking a situation which will leave her feeling continuously emotionally threatened, unless she is superwoman, has a Ghandi-like personality, or... not sure what I'm trying to say here, except that RS seems to have strong emotions which need to be channeled, rather than blunted.
Wow, guys. I feel like a little old southern lady, but honestly, Bless Your Hearts. Several years ago I would have read your posts and thought, "They're doomed." I'm not so deceived now. If you choose to, you can meet this challenge together. As long as your respect and love one another and yourselves, whatever solution you reach together will be okay.