Speechie: Breaking down your post, I note two concerns:
1) "He's not reading fluently" - This does not appear to be a requirement for entry to first grade. My DD's K class required the kids to learn a small selection of sight words, and to be able to read extremely simple books with repetitive vocabulary. The requirement for reading fluency is something they work on in first grade.
2) "I am worried he lacks experience of schoolday structure/routines..." - There's a first time for everything.
In your place, I wouldn't be too concerned.
