>>> So the questions now are:

>>> 1. Is this the original Joker?

Yes, I think that the Comedian must be the original, because he is the one that we know fell into the vat as the Red Hood.

The "criminal" joker looks like the Joker from his first appearance in the comics, so I guess that Comedian Joker created him and had him working out in the field before he himself made an appearance. Also, The Clown seems to be the Joker in the golden age and silver age stories. So, (see the answer to 2.)

>> 2. How many of Batman's previous Joker encounters have been with copies of the Joker?

It may be that Comedian had Clown working in the field most of the time, and Criminal behind the scenes helping him make elaborate plans. That's if there have always been this core group of three. Otherwise I could imagine that Clown is the latest in a series of clowns.

I wouldn't be surprised if Comedian has rarely faced Batman himself up to now. It's definitely him in the Killing Joke and Grant Morrison's Batman run.