Nice work on getting the game done, I played it all the way through but I'm not sure when I was meant to use the rewind mechanic. I only needed it once I was already dead at which point the game rewound anyway! Do you use Cinemachine already? A "look ahead" movement and soft zones to polish the camera work will make it feel heaps nicer and they're easy to do with Cinemachine!
With your parallax, you've got your values around the wrong way. The further away the object is the slower it should move. In your case your mountains in the background are the fastest moving object and they should be the slowest (minus the sky, clouds, etc).