@Eliusa,
You've been with him a long time, you can judge his character. But, can you know deep down inside, "really" how he may feel. Perhaps as a man, he shrugs things off on the outside, perhaps he pretends to know that you "fell asleep on the lounge" but inside he knows that you didn't want to sleep in the same bed.
Perhaps when he finds out, all the things he is hiding inside because "people do that", will come to the surface of his mind and he will think back and know all those "thoughts" he dissed were real and then what?
See if you feel he shrugs things off, then tell him you are in your prime, not happy, but this stud of a guy wants to give it to you, at least you told him right?
You say you are climbing the walls, sleeping on a couch, "think" that as he's a gentle soul if he found out he will only be upset as he was cheated on, not that you cheated. But gentle souls tend to have even more feelings when they come to the surface. I'm not sure Eliusa, if he would not be upset that you cheated you are playing with a full deck of cards and only one needs to fall out of place. You are assuming that he would remain with you, be hurt and feel cheated on but that won't matter because you don't sleep with him anyway you are just friends.
What if he doesn't remain with you? The whole entire family find out, your children.
What if you hurt him so much in his heart and you never realised, you "thought" he'd get over it like everything else?
What if he wants sex, love and not just a friend after all he's how old 50 as well? Plenty of time to find a beautiful love, not just a friendship.
You're a dreamer. You sleep at night on the couch as if you are doing the right thing by this man, not sleeping with your husband. Your husband is sleeping in a bed, waking up and thinking, my wife doesn't love me anymore. You are pretending you just fell asleep you can't keep doing that. People are not stupid, they really aren't especially a "good friend" a good friend can tell in the eyes, the way you dress when you go out, walk.
I think you may be under estimating the emotions of your husband, now and later. I really do.
It's evident you wear the pants here. But kind souls, gentle souls, well they will feel the pain just like a manly man will/does... Yet, if you just walked even for a few months, got this out of your system or realised it was in-deed love, then either way, you were separated, you walked to clear your head and mind and other from all of this, I don't quite see that as cheating but it will give you both the chance to see what you really want in life, love and friendship or sex and friendship because your husband obviously loves you.