Several transpondian references to deal with here:

1)
dr (debtor), Dr (Doctor), with or without a "."
The rule of which Dr Bill has not heard used to be quite firmly the case over here, but is not so any more. We use either form - with or without "." - and no-one comments; not even if one isn't consistent. However, words that have had bits lopped off to form the abbrev. should have the "."

B)
What do we call "."?
Full stop - whether it is at the end of a sentence or after an abbrev. There is no particular justification for this - it's just the way most of us do it. Some people have started to call it "period" but that ain't too common, yet.

Þ) comma, semi-colon, colon
comma, semi-colon, colon

But "!" is almost always called "exclamation mark"
and "?" is a "question mark".

I think that's all for now!