The question is not whether it is considered cheating, but rather, why on earth is your husband doing something that is so hurtful to you? Marriage is built on respect, and clearly, this is disrespectful and dismissive of your feelings. This was beyond innocent flirting, particularly the last part of the comment. I really don't know any loving, mature, committed couples who would find this acceptable.
I am sorry one poster tried to make you feel as though you caused this by "snooping." While marriage is a two-way street with each partner bearing responsibility for making it work, one person doesn't "cause" another's bad, boorish, inconsiderate, childish, selfish behavior. And, I am saying this without even considering the blatant disregard he showed for you that is detailed in your SWH.
After reading your SWH, there is a CLEAR pattern of your husband "checking" out of his responsibility to be a respectful, trustworthy partner.
While everything in life does not require counseling, in this case, it seems you have been hurt beyond the point of just healing by yourself. Go talk to someone about repairing your own sense of self, and then decide what you want to do about your marriage. You may or may not want to work on the marriage, and it is unknown at this point whether your husband will want to do the work to save the marriage.
At the very least, do something for yourself, and go talk to someone. Also, in the meantime, develop other female friendships and interests. Maybe take a class on-line or at a nearby university. Do things that are healthy for you and that make you feel better about yourself.
I am really sorry you are having to deal with this. I do hope you will find support --- new interests and people to help strengthen you during this time.
Best to you.
J. F.