2) joeball, I always maxed opponents in GalCiv2. 9 factions and full minors was around 20? My memory fails me. Anyway, you ask if 9 felt right, try 16. Are you including the minors in your count? By your advice, I'm thinking my 26 would fit on excessive nicely.
I did not count minors; they only occupy a single planet in GCII and as such don't really occupy any significant fraction of the map.
Remember, though, that I'm not sure how much stuff is on a GCIII map relative to a GCII map; my impression is that the density of stuff on the maps (particularly the larger maps) is lower in GCIII than it was in GCII, and that will tend to reduce the number of factions you'd want to have.
3) Either one of you: Do you see scattered vs. loose clusters vs. tight clusters factoring in?
I think that tight clusters has less stuff than loose clusters and scattered has more stuff than either, so yes, I suspect that the cluster setting matters. Loose and especially tight clusters are also more likely to give you open expanses of space between empires, which should tend to keep things more peaceful, whereas scattered should tend to have colonies of various empires in fairly close proximity to one another.
The problem I'm running into is meeting other factions much too quickly. I'd love to wait till turn 100 or so.
Your best shot at correcting this is to either play a larger map with the same number of factions, or reduce the number of factions. There are also a couple of variables in GalCiv3MapDefs.XML which look like they should affect how close empires spawn to one another (PlayerStartSpacingNarrowMod and PlayerStartSpacingWideMod) but I don't know how those work.
I'm actually bringing the possibility of contact up, rather than down, since there are limited systems for the computer to start them on? If my hypothesis is accurate, what star setting, and planet setting will give me sufficient distance from other races, while still keeping total planets around 300?
Scattered should theoretically try to uniformly distribute the stars over the map; therefore, on a scattered map, reducing the number of stars should increase the average distance between stars and therefore the average distance between the homeworlds of empires. However, it may tend to cause empires to find one another more rapidly as they have to expand to more distant locations sooner, causing the empires to stretch out and cover more of the map faster, which extends their range and visible area faster.
With clusters, I'm not sure of the behavior. If the game tries to produce a set number of clusters, then reducing the number of stars should reduce the cluster sizes and increase the space between clusters, which will increase the distance between empires which spawn in separate clusters and reduce the distance between empires which spawn in the same cluster. If the target number of clusters is a function of how many stars are on the map, then reducing the number of stars should tend to increase the likelihood that you will start in close proximity to another empire.