Cam sex is different than watching porn. There is a live person(s) on the other end of the camera, and you are touching yourself and telling them what to do, and they are doing much the same. It's about as close to physical sex as you can get without actually touching.
But that's not really the point, is it? Nor is what we think about it. The only opinion that really matters in this particular case is hers, because she's the one being hurt by it. You could call it a ham sandwich if you like, but if it is hurting her... well that's the main point that needs to be addressed.
This is where "read between the lines" comes into play. My wife and I actually had a little tension this weekend. It started out with her wanting to go out and do something, and I wanted to wait and go later. This didn't sit well with her, and she was unhappy about it. Then she mentioned that I gave her a "dirty look" when she asked about going out. Then she told me I didn't acknowledge some changes she made for me lately. And the hits just kept on coming. Eventually, I had to ask her what was going on?
The thing is, she was venting a lot of her frustrations at me, but the things she was venting about were really just minor irritations. Nothing worthy of starting an argument about. This led me to my next thought... the things she was complaining about, weren't the actual problem. The actual problem wasn't being voiced. That's where some empathy and understanding come in.
I can't remember my exact reply to her, but I said something along the lines of, "So, what I'm REALLY hearing you say is that you are feeling unappreciated and also feeling that you are giving more to the relationship than you are getting back." Which was exactly what she was feeling. It was important that we got there, because if I had simply focused on what was being said, it probably would have gotten worse quickly. I would have started to try and appease her by doing what she wanted to even if I didn't, and my face would make it clear that I didn't want to, and then she would feel as if I'm manipulating her by placating her, and placating her would piss her off more, not make her feel heard and cared about. Do you understand what I'm saying? This is a trap most Waywards fall into. We keep trying to "do what makes them happy" and in doing so, showing that we actually only care about ourselves and stopping the negativity towards us, and not actually caring about their feelings and needs. BS's don't need or want you to make them happy. They want honesty, and integrity, and any sign of actual self-respect that you may have. They don't want their asses kissed, they want a relationship, and they want feel that they exist in that relationship.
Your infidelity lasted for so long, involved so many different incidents, and was lied about (and is still facing some TT) so much, that your wife's brain is on high-bullshit-alert at all times. You could say that it is sunny outside, and she'd need to question if it really is sunny, or pouring rain, because she's can't believe a word you say without verifying it, sometimes over and over. She's a detective now. She asks the same questions over and over because she's looking for lies, looking for changing stories, looking for anything inconsistent or unbelievable. She doesn't want to do this, but our brains think otherwise.
Anyway, my advice is, don't get hung up on the details here. The cybersex itself probably wouldn't be such a big deal if nothing else had happened, but that's not the case. It's not what you did, or how you did it, it's just one more reminder that you and she don't even agree on what "cheating" is, and that must make things seem hopeless to her. It's okay that you didn't see it that way at the time... you can't go back and change that so don't waste effort on it. Rather, she needs to hear that you see it NOW. That you regret it now. She needs to feel that you'd actually feel badly about doing it if it happened today. By arguing about the semantics of it, she probably feels that you are protecting yourself. You probably are.
As usual, I want to remind you that, even though it's still hard, you are asking the right questions and making the effort Bulcy. Don't give up, okay? Keep fighting the good fight. Part of how we show our spouses that we really intent to change is by never giving up, no matter what. Do that, and no matter what the outcome, you'll know you did everything you could.