ANSWER 1:
These days, everybody orders boards through web sites where you specify all those things via menu selections before uploading Gerber files. Sometimes you just check a box that says “Your Standard Parameters Are Fine For Me”. (You may, or may not, find all those standard parameters listed in detail, about three levels of menus down from the Order Page.)
So it’s just an easy-peasy matter of . . . . clicky . . . clicky . . . . tappa-tappa. . . . clicky . . . bleep . . . . boing . . . and when the first time is over you ask yourself, “What’s the big deal?”, and move on to the next project. Just play the odds - more often than not, you’ll never get a call from the test guy who says (for example) “We’ve been evaluating product performance at 150% overload current, and noticed some trace delamination. What copper weight did you spec for these boards?”
ANSWER 2:
In the “good old days” (formerly known as “These trying times”, before they hired a better PR firm) the corporate “Configuration Control” folks would force you to put that information in your drawing before it was released. A paper copy of the drawing went out with the purchase order, and was a binding part of the transaction. In more recent days, various sets of these requirements were maintained as company “standards” and incorporated by reference, or a logical link into a drawing database. (In practice, many of those parameters are identical for dozens or hundreds of board designs used by a company, and can be reduced to a single file of “boiler plate”.)
The “*Dwgs.User” layer from one of my recent boards looks like this:
Forum_Example-Dwgs.User.pdf (90.3 KB)
I pack a *.pdf plot of that layer into the *.zip archive I send to the fabricator. Some vendors read the “Notes” on a drawing like this, and some don’t, so I also copy many of the “Notes” into the “Readme.txt” that accompanies the *.zip archive.
ANSWER 3:
Don’t worry about it. PC boards are, after all, a pretty low-tech, commodity product that’s been in production for over half a century. Most of that stuff doesn’t matter; it just gets in the way of finishing this product on-time. The vendor will know what works best. 
Dale