I'll try to answer your questions in order.
1/ Go buy a Machinery's Handbook. It's a fat green book that has the numbers on any thread you might want to cut. That book was the first thing they made me buy when I started in the trade.
2/ you have to single point turn it in a lathe, if you can't get a tap.
3/Use a broach and a broaching bushing......look it up in the book!
4/Get some dowel pins that fit your tee slots on your mill table.
5/ Use a large angle plate and hang the part off the back of the mill table, then swing the mill head around over the part.