Some Questions

1. Depends on how many your civilization can support before going bankrupt
2. No idea sorry (but the chances are, you will have either destroyed everyone or been destroyed yourself before you get the chance to research most of them)
3. Again, I have no idea how many there are in numbers. Cant be over a hundred, can there? (not including buildings that are upgraded as soon as better technology is researched)
4. Each planet will be unique, BOYAH!

Ships: Agreed, as many as you can support. You'll need a fairly good machine or a moderate level of patience to put up with ten races all having hundreds of ships, but it can be done, especially if you trim down what you watch.

Techs: Quite a few, though being a less military player, I'm more likely to see most of them before endgame than most. Probably well over 100, I think. Heck, you've probably got close to that just for the three branches each of weapons and defenses, so my guess would be closer to 200 techs.

Hmmmm.... (counts include wonders/super improvements, and are all my best recollection, so reality could be quite different)

Farming x3(4?)
Morale x4
Manufacturing x6
Research x7
Econ x6
Influence x3
Misc Wonders x12
Trade Goods x10

So an estimate of 51, which is probably on the low side.

Customization of Planets: Not much beyond placing a building in each of the tiles, terraforming the planet, and giving it a name.

Just a quick foll0wup. Regards to how many buildings on planets is determined by its quality. You get to determine what buildings are built where. Yes you can make an analogy between a colony management screen on GC2 and a city screen in Civ.

Oh im looking towrads to this game as a little child lays in his bed waiting for santa