Keep in mind that I have not seen the final product, so I know only what I've been able to get from the Goodman Games forums and from talking with the designers.
1: They will be using their own fairly generic pantheon drawn from the gods used in the pages of currently published DCC adventures. I am fairly certain they rounded out the list to make a complete pantheon, but its by no means exhaustive or complete. You will have plenty of room to round them out yourself and add your own.
This list was compiled on the Goodman forums. Its not all of them, but at least most of the ones that have appeared in the DCC line thus far.
#0: Myna, goddess of good luck
#1: the rat gods: Nattimuath, Lord of Disease & Nimlurun, Lord of Filth
#2: the Outer Gods
#3: Meelkor, god of humility and piety
#4: Coatlimict, the Xulmec god of war and undeath
#5: Malotoch, the Carrion Crow Mistress, goddess of cannibalism
#7: Pelagia, minor goddess of the sea, music, and travel
#8: Tororthun, drow goddess & Bargul, deified drow heroine
#11: Crypticus, god of secrets and forbidden lore
#12: Gorhan, god of valor & Aristemis, goddess of strategy
#13: Justicia, goddess of merciful justice & Chaotor, minor demigod of betrayal and chaos
#14: Honorus, god of might and honor
2: From what I've seen the authors have worked hard to add detail and leave enough for the players to add what they want. I think you could add any of the things that you mentioned without causing any problems at all.
3: Yuan-Ti were used in Curse of the Emerald Cobra (an excellent adventure, by the way), I am not sure if they are just called Snake-Men because of the copyright issue or if they are referring to something else. I know that there is a Freeport DCC, so its possible they are referring to that.
4:Yes, there was a Freeport DCC module so I'm fairly sure that it will be included in the campaign world.
Eric,
I don't know about any current CC2 maps from those products. I don't own them myself, if I did I'd whip some up for you.
