So I've been exploring the playbook site that the Jets pb came from (because I'm a playbook nerd).
For a ton of the questions you have, the Baylor 2006 defense is very good at explaining the terminology (although there are a ton of typos... because Baylor).
The first few pages discuss alignment, numbering, coverages and names of formations.
This is all good stuff. When you get to the names of formations, just understand that there are a million different names for each formation. For instance, what the Chiefs calls SLOT, I call Twins, and Baylor calls Twins I.
http://www.footballxos.com/download/...42-Defense.pdf