I have been the woman in this story, and eight years later "Bob" is gone. Our marriage is excellent. My husband is my best friend and I rarely, if ever, think about "Bob."
Shortly after I got engaged, a new coworker came to work with me and we fell instantly in platonic-love. The experience is almost indescribable, and distinct from falling in love romantically. There's less sappy oxytocinness, less of heart-fluttering excited nervousness, and no physical attraction. Instead, it just felt like we were instant best friends who shared, and perhaps since birth had shared, a brain or even a "soul." The only experience I've read about that sounds even comparable is the attraction experienced by siblings raised apart who meet as adults and often fall madly in love because they have so much in common.
As it turned out, this was a pretty similar situation. Coworker and I had grown up in the same small town, attended the same college, the same grad school, had chosen the same profession and even had tons of mutual friends, but due to random fluke circumstances had never met. We had almost identical personalities, mannerisms, likes and dislikes. Within hours of meeting one another, we could finish one another's sentences.
Everyone at our office thought we were having an affair, and it was a bit awkward. My then-fiance became suspicious and tried to bar me from seeing Coworker. I acceded but continued to see Coworker behind Fiance's back. I couldn't give up my best friend.
Coworker and I were an excellent team professionally and began to travel together for work. One night, he became tipsy and made a tentative pass at me, which I brushed off. Months later, I got drunk and flirted with him, and he (sober that time) talked me down. We were both glad we never did anything, but the risk was definitely there.
He transferred to a foreign office in another time zone, and our contact dwindled. Oddly, this wasn't painful. The rush from bonding so instantly and totally with him had faded, and our obsessive desire to talk to one another constantly cooled to more of a normal friendship. We still keep in touch sporadically.
If this is akin to OP's situation, there may be some hope for his marriage. If Bob and the wife are already sleeping together, OP is done.