I agree that it is normal to get fed up in a long marriage, but I imagine that the reason people speak so passionately against affairs is because of the pain the deception causes.
Deception, when it happens to you, is rather more than "quite a big deal" - and the reason people "put up with it" (I assume Butterball you mean, the deceiver, since by definition, the deceived don't know there's anything to put up with) is because they are not brave enough to risk losing what they have. Ultimately, it is a wholly dishonest behaviour choice.
Denying someone choices in their lives is wrong. If the OP's husband knew that his wife had reduced their marriage to this, he might decide to withdraw the security and trappings that the OP currently enjoys - but currently, he cannot make that decision, because he is being deceived. I imagine that most spouses would come to only one conclusion if a lottery win would be enough for their wives to leave them - and the affair partner might also take a dim view of his financial standing being of such great importance to his paramour.
It also bemuses me when posters blame sites like Facebook for their own behaviour choices - as adults, we have to take responsibility for our actions. That said, it amazes me how many people are getting themselves into so much bother with this particular site.
OP, the most liberating and honest thing you can do in this situation is to tell your H what has been going on. I do understand how a huge weight loss and an old flame can be an intoxicating mix and while I don't relate to your thought processes and justifications, I do understand this.
But the way you are behaving just isn't fair - and perhaps people are reacting to you with a bit of harshness is because you don't seem to express any guilt for your deception (that and the "lols" !
If a man posted on here that he was having an affair and the only thing keeping him with his wife was the lifestyle, I can imagine the reaction. If he went on to add that if the OW won the lottery he would be off like a shot and wondered aloud why he couldn't have a "bit on the side", well, what do you think would happen?