You admit you have played excessively in the past and your girlfriend's nerves have been rubbed raw due to the resulting neglect, apathy, and failure to meet her needs, that no amount of moderation will result in a reasonable response from her until you prove that it actually is in moderation. (No matter which way you slice it, playing 20 hours a day is not compatible with a healthy relationship) And, depending on your circumstances and how you are playing, 35 hours a week may not be moderation.

I have been there, many years ago, in college. I basically had to stop playing entirely for a period of time to let the wounds heal, and then when I came back, it was with a much more balanced approach.

It's not even about the number of hours you play so much as, are her needs being met. I'll tell you one thing you say that I find troubling:

"I don't drink anymore, I don't gamble, I don't cheat, I don't
beat her.. I play CF, that's it."

Is this what you believe qualifies you as an adequate boyfriend? If you do, you must expect her to have exceedingly low expectations. Presumably she has needs in the relationship. You need to meet those needs first, and play CF (or whatever other hobby) only after. If you are, for example, ignoring (or not even hearing) her when she tries to speak with you while you are engrossed in CF (a bone my now-husband used to pick with me, and still does once in a while), she is going to feel neglected, ignored, and generally unloved. This may mean reducing your playtime, it may not. It may mean scheduling "game nights" for yourself when you can make it clear that you are "otherwise occupied", and/or playing when she's not around, and filling her needs in other ways (bringing her flowers, cleaning the kitchen, taking her son off her hands for a while, etc.) It may mean simply accepting that you have to sometimes link-die or idle your character and accept the consequences so you can turn and pay attention to her when she needs it.

Sorry, but "Not beating her and cheating on her" doesn't cut it for any woman with even an ounce of self-esteem.

Now at the risk of sounding like I am just siding with your girlfriend, it doesn't sound like she's been the most effective communicator about this either, or that she's been taking any reasonable action to make things better in your relationship.

But you can't control her, you can only control you. Right now, you are both just blaming each other, and you'll get nowhere until either you or her is strong enough to lead the situation somewhere productive (and hopefully, the other will follow.) It takes two.

I can guarantee you if you just fold your arms and say "It's my hobby and she's just jealous and I'm going to play as I damn well please" the relationship is either over, or you are romantically involved with a doormat.