From where I'm sitting, it looks like death should not be the end in that case.
You can't perceive the passage of time when you are dead, so you're just going to experience dying and then immediate rebirth after the countless eons pass for that rare moment where entropy spontaneously reverses to form your mind again.
Again, my point is that (1) we can describe reality from the perspective of any physical object in the natural sciences, independently of whether or not it is a mammal with a brain, (2) I can experience the reality of the perspective in which I occupy directly for myself, and (3) it seems rather intuitive to then conclude that all possible descriptions of reality from all possible perspectives also correspond to an actual reality from that perspective (i.e. each possibly description of reality from any possible perspective also has a corresponding "what it is like to be" in that perspective).
Rejecting #3 seems to fall into solipsism since you would only be left with the reality from your own perspective, and descriptions of other perspectives would not have a corresponding reality to those descriptions. Accepting #3 would assign reality to all possible perspectives, and thus there would no reason to treat mammals with brains as anything special requiring a special explanation with some special "consciousness" property, since the physical sciences allows us to describe reality even from the perspective of inanimate objects like rocks.
It is clear you need an additional fourth premise to insist that mammalian brains do something special that requires a special explanation, and I do not see what that fourth premise could possibly be.
As I said, experience is just the reality of a particular frame of reference. To ask why there is a reality to it, you are just asking why there is a reality rather than no reality, i.e. not much different than a "why is there something rather than nothing" question. It cannot be meaningfully answered. You can explain why something in reality exists, but then whatever explanation you give will still deal with aspects of reality, which you can then just ask why those aspects exist, and repeat this as an infinite regress, constantly asking "why" to every question. At some point, you just have to respond, it is what it is. Reality as a whole cannot have an explanation. It just is. You just have to accept reality is as a start point or you will never get anywhere.
Experience is not something created by brains. Experience is, again, just reality as it exists from a particular perspective. Brains play a role in what we experience, but so does everything else as well. Every object we posit to exist, including our brains, play some predictive role in allowing us to explain and forecast experiential reality. But none of these objects create reality, as if reality is something that is "given rise to." Reality just is. We can identify objects within reality and use those objects to explain and forecast reality, but none of them can possibly play any sort of creative role in giving rise to reality itself. Logically, it makes no sense, as it is reality which grants objects the quality of being by definition.
I am not a fan of the interchanging of "experience" with "feeling" as you are using, kind of like when you also interchange it with "consciousness," because these words like "feeling" and "consciousness" clearly have human-centric implications to them. This is obvious if we apply these different words to inanimate objects. It clearly has rather mystical implications to say things like a rock can "feel" or it has "consciousness." However, to say the rock can have an experience is part of everyday language, i.e. "the rock is experiencing erosion in the rain," or "the rock is experiencing fluctuations in temperature." The word "experience" just means to undergo a real event, so this kind of language is rather natural, while assigning "feeling" or "consciousness" to a rock seems to anthropomorphize it too much.