At this point, yes. That is the only possible explanation I can come up with for JL being 100% against voting for you when he is 100% insistent you are scum. I cannot fathom any other scenario where this would be the case, and I have looked and looked at this from every angle I can imagine. JL is your sacrificial goat (lambs don't have horns like he does). Town lynches JL like you want, JL shows scum like you know he will, and you are the instant town hero. Perfect cover. Mayor investigating you will do nothing as you will only show as mafia, and the mayor cannot reveal themselves. Even if they have a communicating innocent reveal you are scum, who would believe them? With as many mafia as are left, it could be easily dismissed as a mafia ploy. So now you've gained the towns trust, yet another investigation to possibly find the real policeman has been thwarted, and you get to search for more of your scummates.
At this point I do not trust anyone but myself. My theory is sound and the only plausible explanation for JL's behavior and your accusations. I did not post this theory lightly as I realize it is quite complex. I applaud both you and JL for the elegance of your plan. It's really quite beautiful, if you're scum.