If you're capable of loving two people without it diminishing your love for either, you do, in fact, have poly tendencies, it's not a "twisted justification". You just made a mistake. So what if L would be scared? Is your husband a shotgun-wielding hothead? He's been much more understanding than you thought he'd be, he's even shown signs of compersion (positive feelings about your partner feeling love for others, the opposite of jealousy). Why assume he couldn't handle the truth? Isn't that insulting to him? Wouldn't he *want* to know and don't his feelings matter? Won't it be much, much worse if he finds out in some other way (talk about something to be scared of... *that* is a much more explosive scenario in my mind, much harder to get over, and these sorts of things are notorious for coming out one way or another)? What if he somehow finds this very thread?
Food for thought. Moving from cheating to poly is actually not uncommon at all. But it requires a strong base of trust, which means, ironically, revealing that you were untrustworthy in the past. I can't promise it will go well, but as I've said a couple of times now, if you don't do it yourself you choose to live with the specter of it going far worse at a future date not of your choosing. And hey, you haven't had intercourse, which seems to be especially triggering for men in these sorts of situations, so there's that on the side of it potentially going better than you think.
It is, of course, your choice, but wouldn't you rather be the partner he deserves? I myself have cheated, revealed it, and been forgiven, so I know of what I speak. Instead of dwelling on this painful love that you're choosing to assume can't be ethically consummated without even finding out for sure (gotta say, that's the coward's way out, especially if you really do love him), or dwelling on the fact that you did, indeed, make a mistake (who hasn't?)... you could just do the right thing.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.