Welcome to the forum Sculptor,
There is a lot of good info on this forum, but the traffic is somewhat light. Sometimes I only check for new posts every couple of months.
Here are some answers based on reading and web searching. Hope it helps.
1) There are basically 2 different tooth profiles used on clocks and watches. They are either involute or cycloidal. Both roll along a single contact point without sliding, so friction is low. Old hand cut gears were usually cycloidal. Modern gears are usually involute, possibly because they are easier to cut by machines. I recall reading somewhere that involute gears are more tolerant of continuing to operate with spacing errors that might occur as the clock bushings wear out.
2) No idea. I could see some advantages with very nice looking color options. Personally, I prefer the look of natural wood.
3) A wheel that is double the diameter and thickness will weigh 8X as much. This might imply that it would take 8X as much energy to move it with each tick. However, the pendulum friction remains the same. The escapement could still be left small to reduce energy requirements. I would guess that the weight requirement for a 2X larger clock would be bound between 1X and 8X and probably around 2X.
4) The calculations for the train are fairly straightforward. Search for recent posts here and you will see some examples. You will eventually need a gear designer. There are a few of them out there in the $100 or less price range. I have been successful using a free gear tooth profile generator at
http://woodgears.ca and exporting it in a file that I could upload into my CAD program. I clean up a single tooth and array it around a circle to produce the entire gear.
Steve