Glad you posted this, Ella. I follow your writing with pleasure, and I learn a lot. As you yourself point out, your belief in the multiverse is just that, a belief. But it is not the same as religious faith, I think.
First, faith itself requires doubt, otherwise it is certainty. If you meet believers (including atheists) who say they have no doubts, then their faith is innately wrong.
Second, concerning Popper's falsifiable criterion, it certainly works in physics. But it also works in theology. A lot of what you object to is false and provably so.
Third, does poetry convey truth, and is it falsifiable? I don't think so, although there are bad, mediocre, good, great and classic poems. Faith is more like poetry than the thermodynamics.
Finally, Jesus had some of his harshest words for people who try to make converts ("you only make them twice as fit for hell as yourselves"). No one can convince you of God but God, and that happens (if it ever happens at all) by a relation established by God and accepted by you. It is something like falling in love.
Keep up the great work!