"I do not believe in anything until it has strong and concrete evidence, especially experimental evidence"
"I believe in B-theory because it is a physical fact about the universe and it has experimental evidence (general/special relativity"
Do not agree with:
"A-theorists are aware of these criticisms, and there are many counterarguments. Some influential A-theorists are A.N. Prior, E.J. Lowe, and Quentin Smith. Some influential B-theorists are Bertrand Russell, W.V.O. Quine, and D.H. Mellor. The A-theory is closely related to the common sense image of time, and the B-theory is more closely related to the scientific image. Proponents of each theory shoulder a certain burden—explaining not just why the opponent’s theory is incorrect but also why it seems to be correct to the opponent."
Not only is A vs B series of time not an experimental fact, but you want to say time doesn't exist, it is eliminated!
There are notions of timless physics, but that isn't what you were getting at. There is of couse still time in any static/eternal multiverse or universe. Time is difference/change as Julian Barbour says. There is still difference between each snapshot of a block universe with stuff in it like ours. Maybe what you were going for is the flow of time is a conscious illusion in block universes. So psychologists have to explain why memories give us such a real sensation of "now".
You go on about experimental determination, but what are finite observers such as us supposed to determine empirically when we are limited by the speed of light and other finities? All of your conclusions and their alternatives are compatable with the known laws of physics. We may never be able to conduct a decisive experiment.
And lastly, one problem unqiue to static universe theories, where all moments present, past, and future have no privelage. Why am I experiencing right now, 2021, and not any other of the infinite other moments with conscious observers? If this moment has no privelage, why is my observer moment not in the future where the population is certainly higher and thus an observer moment at random would be more likely to occur?
I've focused on time mostly, because it exists and is the obvious hole in your conclusion. Causaility and free will deserve lengthy discussions, but again realize we may never experimentally determine any of these. We are limited in what experiments can be conducted; we are finite.