a lot of the answers to your questions are floating around the site, so make sure that you have a look through.
to answer your question:
the difference between Italian and British BB is the threading. the spindle length of the BB will also affect the chainline of your bike, so the cranks should match up to the spindle on the BB.
to fit the bars onto the cinelli stem, you basically have to slide the bars in. i tend to use a flat headed screwdriver to "wedge" the stem open a bit more so you can slide the bars in a bit easier. take your time and don't force it.
the ratio depends on where you live and your preference. in london, i know people that have everything from 68-78 gear inches. there won't be any problems running a road crank as singlespeed. again just make sure that you have the right BB.
as for books: http://icelord.net/bike/ might get you in the right direction. again, not sure how detailed you want to get with regards to your books. you can get everything from a book of bikes to lust over to something that is essentially a technical manual. but most of the technical answers are on the forum because you've got a lot of very skilled people on the site.