Tommaso -
Thanks. While I was thinking about #2 (which I now see your essay did answer), I suppose #1 is actually the more pressing concern, and I am much relieved with your reply!
The MUH does become much more understandable when we discard all assumptions of continuity. If we are indeed in a finite universe (planck units - finite number of states) then everything becomes computable (although some computations may take a long time.....). No infinities to worry about! Of course, that's not quite what Tegmark seems to say ...
If this is the case, what is the ontological status of mathematics, its theoretical continua and infinities? Mere symbols without content? Epiphenomenal finite brain states? And (this may be a dumb question) what is the hardware on which the computing algorithms are being run, and where did that hardware and those rules come from?
With many thanks, and sincere respect - George