First, here is thread where you can download the manuals for Pinball Dream I, Pinball Fantasies, and Pinball Illusions:

http://www.gog.com/en/forum/pinball_gold_pack/rules_for_the_tables

Question 1&2: As far as I know Pinball Dreams II and Pinball Illusion don't have an option menu and so no option to choose the number of balls. And you can't change the resolution in both of them.

Question 1: Since you can't increase the resolution, you have to memorize the layout of the tables. Now you know why older games are harder than the new ones: You have to see beyond of what's going on the screen ;-)

Question 3: To be honest, I don't play these games very often. I prefer Pinball Fantasies. But what I noticed is, that in order to reach the higher parts the ball needs to be in movement and you have to hit it with the lower end of the flipper. Maybe some more experienced players can give additional advice.

And a personal advice from me, although I might get flamed for it on this board ;-)
You are saying that you are new to pinball simulators. I don't know if the Pinball Gold Pack is the right point to start. If you'll ever get your hands on a real pinball machine you'll notice the difference right away.

You should have began with the Pro Pinball series:
http://www.gog.com/en/catalogue#all_genres/search/pro%20pinball/

I know it's only one table per game, but the (physical) accuracy is higher, your view on the table does not get obstructed by ancient hardware limitations and it offers basically a richer gaming experience.

I just play Pinball Fantasies mainly for nostalgia reasons. :-)
Just noticed that you posted your questions 3 months ago. Well better late than never... ;-) I hope my answers are still somehow useful.