Let me ask the question a different way.
(becuase I had all those same arguments with myself when I cheated and I know the ultimate outcome)
Is your relationship with your husband so meaningless to you-that you are willing to forsake the foundation upon which it is built-in order to protect L?
I say it that way for a reason.
Relationships are built upon trust. EVEN IF HE DOES NOT KNOW IT-you broke that trust. The fact that he doesn't know it, doesn't change the reality of it. There IS a huge crack in the foundation of your relationship now-which means-it's more susceptible to failure.
You can leave it (I did-for years-not pretty) and you may get away with it for a time. But, eventually, the consequences will show.
The problem with that choice is-that each day you allow it to remain hidden-will be another level of resentment built when the truth comes out. So, what may be somewhat easily forgivable now-could end up being too much to overcome later.
As for L-
I do understand some of what you are saying. In our case, my lover had helped ME raise my oldest child and was already close to the middle child (youngest wasn't born yet). My husband DID get violent and LITERALLY tried to kill him the first time.
Coming clean 7 years later, that the affair had continued-risked my lovers LIFE and risked all three children losing him in their lives (the youngest was born by then). The youngest is his BIOLOGICAL child (this was not a secret or part of the affair).
So the risk was HUGE HUGE HUGE.
It did mean putting a lot of responsibility on my husbands shoulders-to make a choice to do the right thing for the kids-and not the right thing for HIMSELF. Which wasn't fair-but it was a consequence of my choice to lie (by having the affair in the first place). I had ALREADY chosen to NOT put the kids welfare first BY HAVING AN AFFAIR-regardless of how discreet.
My husband chose to put the kids first.
Then he changed his mind some... I don't know-100 times? Over a 2.5 year period.
But, in the end, love won out.
We succeeded in putting the past behind us and building a family together (boyfriend included) because ALL THREE OF US took the high road. There were many months of discomfort and torment for my lover and I. The sheer terror of what trigger might send DH through the roof and result in someone being dead. The wondering what was going to happen next or if we could get through it. The months of not touching, not talking, seeing each other every day, day in and day out-but literally not speaking or touching was hell.
But-we did it because those were the steps we needed to take to re-earn trust and prove ourselves changed from the liars we were before.
I used to say that if someone cheated-they should take it to their grave, because confessing was selfish.
The reality is-cheating is selfish. Once you've done it-you already chose to be selfish.
If you found out today that you had HIV/AIDS, would you tell your husband?
WOULD HE WANT YOU TO TELL HIM?
It's no different. You owe it to him to be honest and to give him the respect, honor and privilege he's earned as your husband-to decide how he wants to handle the information.
"Love As Thou Wilt"