Hello there
The plan laid out in the book is a guide.
It's really good to follow your baby and use that as an outline.
Not all babies following things to the book, most don't.
When he wakes up at 45 minutes, what is he doing?
If he is that tired, maybe wait until the next sleep phase to wake him up so he's not so grumpy.
Also, with moving to the 4 hour EASY all babies need different things.
Some need a slow transition, some move over cold turkey.
Just do whatever is best for your lo!
Melissa