Well, of course there's an open question. Nobody has yet shown that a simulated neuron is exactly equivalent to a biological one; its generally assumed this is the case, but even simulating c. elegans brain won't show this 100%. I would also suggest that it is more correct to say your number S, as a representation of state, has felt (past tense) pain or whatever, but to suggest it is currently feeling anything would be to privilege some part of the number over another - although I'm not sure exactly how to be more rigorous about that?

Suppose we replace 1 of your neurons with a black box that still chemically interfaces with your other neurons, but comes up with the decision about what to do in silicon. If you had a switch to flip back and forth between that black box and the biological version it replaced, your consciousness would not change as you flipped it back and forth - the same is true for replacing a few hundred, thousand, million or billion neurons: if the parts behave the same, the whole behaves the same.

so imagine flipping that switch back and forth -- or better, imagine that I'm in front of you flipping it back and forth, but you don't see the state of the switch, and your neurons are biological sometimes but sometimes simulated (it's just a hypothetical, this isn't an actually possible machine). You can't even tell the position of the switch. You feel and report pain the same way, consciousness too. Would you really say that when the flip is switched to simulation, you don't really feel what you report feeling? Of course not.

I think it's illusory to talk about the direction of time. The reason we do it this way is causative. The reason I say S "is feeling" pain is if you continue to simulate the next few quadrillion states, it ends up expressing/feeling those subjective feelings. In another sense the tense we use doesn't matter at all.

I'm not sure what you're saying about privileging numbers - what does it mean to privilege a number?