The question at the end seems like it presupposes that there's some invisible baton that gets passed around between different copies of you.

When you go to sleep you imagine the baton being passed from your sleeping self to a copy who's having the same experiences elsewhere in the (hypothetically infinite) universe. And then you ask "But what if that copy forgets to pass the baton back to me when I wake up?"

But of course, there is no baton. This should be reassuring, because if there's no baton, the baton can't get lost or misplaced :D You wake up as yourself not because every night the baton manages to make its way back to you, you just wake up and the baton doesn't exit.

Dreams have features that make them different than reality. If you for example look at a clock two times in a dream the clock does not behave the way clocks in real life tend to behave. A clock in real life has object permanence and keeps it's state in a way that a dream clock usually doesn't. 

People who train lucid dreaming have a variety of tests like that for telling the dreaming state apart from the normal reality. 

Object permanence where objects are able to exist independent from you looking at them is a key feature of physical reality and a world like the dream world that does not have that clearly is not physical reality.

Just because you don't notice when you're dreaming, doesn't mean that dream experiences could just as well be waking experiences. The map is not the territory; Mach's principle is about phenomena that can't be told apart, not just anything you happen not to notice the differences between.

When I was recovering from a psychotic break in 2013, I remember hearing the beeping of a crosswalk signal, and thinking that it sounded like some sort of medical monitor, and wondering briefly if I was actually on my deathbed in a hospital, interpreting the monitor sound as a crosswalk signal and only imagining that I was healthy and outdoors—or perhaps, both at once: the two versions of reality being compatible with my experiences and therefore equally real. In retrospect, it seems clear that the crosswalk signal was real and the hospital idea was just a delusion: a world where people have delusions sometimes is more parsimonious than a world where people's experiences sometimes reflect multiple alternative realities (exactly when they would be said to be experiencing delusions in at least one of those realities).

To run with the spirit of your question:

Assuming the Dust Theory is true (i.e. the continuity of our experience is maintained purely by there somewhere being the next state of the state-machine-which-is-us). It doesn't need to be causally connected to your current state. So far so good.

What if there is more than one such subsequent state in the universe? No problem so far. Our measure just splits, and we roll the dice on where we'll find ourselves (it's a meaningless question to ask if the split happens at the moment of the spatial, or the computational divergence).

But what if something steals our measure this way? What if, while sleeping, our sleeping state is instantiated somewhere else (thereby stealing 50% of our measure) and never reconnects to the main computational stream instantiated in our brain (so every time we dream, we toss a coin to jump somewhere else and never come back)?

One obvious solution is to say that our sleeping self isn't us. It's another person whose memories are dumped into our brain upon awakening. This goes well with our sleeping self acting differently than us and often having entirely different memories. In that case, there is no measure stealing going on, because the sleeping stream of consciousness happening in our brain isn't ours.

https://space.mit.edu/home/tegmark/crazy.html Large universes put some subtleties into the meaning of "real" that aren't present in its common usage. 

Decision theory-wise, caring about versions of yourself that are inexorably about to dissolve into thermal noise doesn't seem useful. As a more general principle, caring about the decisions you make seems useful to the extent that those decisions can predictably change things.

My dreams have none of the consistency that allowed smart people to figure out the laws of nature over the millenia. It might be possible for a superintelligence to figure out how to make decisions within a world working on dream rules which had predictable future effects, but I believe it to be far beyond my powers.