Hey I'm glad that you find this interesting! I'm not really subject area expert on Islam or Islamic finance; just picked up a few things here and there from studies and from work. Honestly a bit surprised that I have this much to say about it, especially from the angle of Marxism.

And don't worry about convincing your hypothetical Muslim interlocutor about the truth of the immortal science or whatever; even if they're not convinced into immediately converting to secular communism, if they truly are arguing in good faith and with intellectual curiousity, they'll probably arrive at some general position about their own religious belief and practice that would lead them to do some good in the world.

Go get some sleep!