I agree with all of the above: Don't tell him you know about the Tinder profile, just tell him you know these are lies and will not tolerate them anymore. Then move on to the next topic. I'Ve seen this advice around here.
As for the timing of the meeting with H, it would be good that you meet with your L before to at least answer your current questions, but I also strongly agree that you should just go in there to listen. As much as you expect this to be about the ending of the M, it will hit you if it is the case. You need to absorb the shock before making any decision.
You sound like you're in a good place to do all of this.
M39 D6 D3 (at S) S 2014-09 D 2016-09
"You can't start a fire sitting around, crying over a broken heart" - Bruce Springsteen.
