There are two issues here...
1. Yours
2. His
Let's talk about 'his' first.
He is obviously trying to justify his affair by using your 'crush' affair. That is wrong. Because he is blaming you for his affair. His affair has nothing to do with you. Even if you had full blown affair, that doesn't give him any reason to cheat on you. It gives him reason to divorce you and get out of your life but not to cheat on you because it serves nothing and nobody. Infidelity not only scars betrayeds but also waywards. Cheating never solves anything. No issues of marriage has ever been solved by adultery, even past adultery of a partner. So, don't let him blame you for his bad choice. This only shows he is not remorseful of his actions and thus, he is not a reconciliation material yet i.e a safe partner.
Did he ever raised concerns about your relation with your C during the time you were close to that guy?? If not, then why didn't he raise any concerns?? Two explanations:
1.I believe the reason he didn't raise concerns was because you didn't cross any line and were fully transparent with him as you claim. So, he had no reason to consider that as an 'affair' and hence, didn't complain about your friendship to avoid angering you and being seen has jealous and insecure husband.
2. It's also possible that like you, even he didn't know what EA was until recently and hence failed to recognize what was going on between you and C. So, he failed to raise any concerns.
Whatever the reason may be behind his choice of not raising his concerns, one point is clear that they have nothing to do with his affair. As long as he persist on his attempts to interlink these two separate incidents, it makes it very clear that he is non-remorseful.
The right thing for him to do was to communicate his legitimate feelings and concerns with you. This would have solved many problems. But, no. It bottled all his feelings and let them turn into resentment and finally used them to justify his affair. This is a behavior of destructive character. He must come out of this for this R to work.
Your issue: there are two important steps to avoid failing into affair trap.
A. Not to act on tempting affair feelings/attraction.
B. Avoid/Prevent the opportunities of affair from raising.
You followed first step very well but utterly failed on second. You knew you had feelings for him. C knew he had feelings for you. You both knew you had feelings for each other and so, your husband. You claim there was sexual tension between you two and all three of you knew about it. I can definitely imagine how insecure and painful your husband might have felt knowing through his guts that you were walking on slippery slope and you weren't avoiding that. You only focused on not falling but not on avoiding walking on that slippery slope altogether.
You had plenty opportunities to avoid being in close proximity with him and had many opportunities to turn this dangerous relation into 'just professional' one. You could have avoided getting drunk with him when your husband wasn't around. You could have avoided traveling alone with him on business if it was an option. You could have avoided sharing personal things with me because they obviously and inevitably build a bond. You could have kept your phone contact with him only to work related. All of these acts would have shown you as a person actively avoiding situations that would create opportunities to push/cross boundaries. Unfortunately, you didn't avoid these situations even when you could. And even more unfortunate that your husband was a witness whenever you made these choices of not avoiding such situations. He SAW you actively making choices that would put you in a situation where you could easily cross the line. He might have believed that this is what you wanted because repeated actions demonstrates inclinations. And, unfortunate for you that he was never there to witness you not taking upon those opportunities to cross the line. He rarely witnessed you following STEP 1.
In short, he was there to witness you making choices that would put you on a slippery slope but he wasn't there very often to see you making choices to avoid falling. His current opinion and assumptions of what happened between you and C are based of what he witnessed and not what he didn't witness and also partly to get away with his affair (dont let him get away). Perhaps, a polygraph test could absolve you from his suspicions.
Coming to your question - whether it was EA or not??
Was I interested? yes. Did I contemplate leaving my H for him, yes, I fought with thoughts of that for a long time
I believe in your case, this is the moment you should have realised that your slippery friendship has become an EA because you partly desired 'Yes' to leaving your husband for C. Which means he had conquered enough space in your life for you to contemplate leaving her husband but that space wasn't big enough for you to actually commit leaving your husband.
You claim you fought those thoughts for long time?? Care to explain how you fought those thoughts? And why it took long time?In your post, I don't see anything hinting at you doing something to fight those thoughts. You let this relation to grow without any resistance from you till he became a desirable option in your life. This was EA, no doubt. You didn't follow STEP 2 because C wasn't just a crush. He was more than that. And, your husband knew it.
[This message edited by Lurkingsoul12 at 5:27 PM, Monday, November 20th]