I think he was claiming by introducing the multiverse that there is no reason to suppose that the multiverse has not existed forever and that therefore there is not need for a First Cause.
What evidence is there for a multiverse?
What evidence is there for the Big Bang? Quite a bit, I think.
Is there more evidence for the Big Bang than for a multiverse?
I assume so.
However:
"2. Unprovability is an absolute quality. I.e. one thing cannot be more or less unprovable then another."
How are we supposed to know if something is "unprovable" or not?
I guess you mean, (1)unprovable unless some new evidence turns up any minute now?
Or do you mean, (2)that the existence (or non-existence)of X is unprovable in a logically necessary way, and therefore absolutely unprovable--in other words, that there can be no possible evidence in our wildest imaginations that would prove that X existed or did not exist?