There's several new threads here. The "Reader's Digest" version-
1.Shimming is not the proper way to bed the fore end - there should be articles existing on this subject. Definitely ought not be a shim on top!
2. The N22 marks are the manufacturer's ID code- Britishwood, I believe.
3.The '44 on the barrel appears to be the manufacture date of the barrel- it also appears to be of British origins, but my monitor is not very good.
4.The elaborate proof marks were done when it was surplused from service.
5. Penciled serial numbers are common on converted rifles- made it easier to put the bits back on the rifle from which they came.
6. Cracked fore ends aren't uncommon and should be properly repaired for best shooting results. Maybe you can combine this task w/ the bedding procedure. Probably an article on this repair is in the library, also.
Look through these! Lee Enfield On-line Knowledge Libraries (Index of Articles) - Military Surplus Collectors Forums
Yup, there's a bunch to wade through...