Whew, so much to write!
1. AFTA: as far as I see it, the following have publically announced membership: Africa, Austria, France, Norway, Russia, UK.
In other words, the following aren't in it: Germany, Rome, Spain, Turkey.
Remember, this doesn't mean we can't have good relations or even trade with non-AFTA people. Just that trade with them is done "at your own risk" - they haven't guaranteed publically they won't steal from all AFTA members.
1A. Let's confirm about Austria though - Austria, are you still a believer in AFTA, after losing $1 in trade? Do you agree with my math detective work?
1B. It looks like 2 AFTA members - Russia and Norway - may be ... umm ... how shall I say this ... close to hostilities should diplomacy fail. Yeah, that's it.

We obviously can't expect them to observe free trade with each other, while fighting each other on the battlefield. So let's make this exception - if you are at war with an AFTA member, or clearly close to war with an AFTA member, you are not obliged to trade with
them. You still have to observe free trade with all other AFTA members.
So, in this case, Russia and Norway can't expect free trade with each other, but each should still expect free trade with Africa, France, UK, and (if Austria is still in AFTA), Austria.
Sounds good? Makes sense?
2. Roddy: do Austria and Spain "know" they're NPCs? In other words, do they automatically support each other, trade with each other, get offended if the other one is attacked, that sort of thing?
2A. Do they ever attack? In other words, if you leave your border with one of them open, is it safe? Can we make a defensive alliance with one of them - "you'll attack my enemy if I am attacked"? Can we make an offensive alliance with one of them - "lets you and me go conquer Bob"?
3. Rome: I'd like to take you up on your offer to mutually build up 26 to a city, and share the costs and the profits. Each turn you'll pay half
rounded down.
So, turn 1 (this turn), we'll build a town. That costs $2, you'll pay $1.
Turn 2, (next turn) we'll build a military base. That costs $3, you'll still only pay $1.
Turn 3, we'll build a city. That costs $5, you'll pay $2.
After that, turns 4 and forever, from the $3 the city brings in, you'll get $2 each turn, I'll keep $1.
Agreed? If so, this essentially means you wouldn't get your $1 this turn and next turn, since they'll be your contribution to the town and military base, and in 2 turns, you'll actually have to send me $1 as the other $1 of your contribution to the city. But after that, you will be making $2 per turn.
If not, then I will send you $1 each turn, as we agreed, and anything I build will be at my expense, but at my benefit.