Hi Corksniffer, good questions. Kit looks great. The bridge bushes will be hard to remove if you drive them all the way in. Just push them in by hand should give you a good indication of the neck/string alignment.
To glue the neck use Titebond should be available from your local hardware or the big blue shed sell it
https://www.masters.com.au/product/9...ood-glue-473ml

Up to you if you glue the neck early in the build you need somewhere to hang the whole guitar to cure and will be more awkward to work on. Generally you will get a better finish on the neck/body join.

There are wipe on satin poly products, some forumites have had good results from linseed oil. I haven't used either so can't really comment.
Good luck with the build !

If you are going to glue the neck soon check the string action will be ok, allowing the bridge will be prouder than when finished