1) Is there any difference in cost between building a Settler in a Town sans Granary and one in a City with Granary? AFAIK it's 30 Shields and 20 Food either way; why would having or not having a Granary make any difference? And how do you figure a Settler costs a total of 70?
Growing one more point of population costs 20 food in a town, 40 in a city and 60 in a metropolis. With a granary you regain half of that amount upon growth. Hence in a town with granary it is only 10 food per population point. For a town sans granary and for a city with granary it is 20 food per population point.
So in the example a settler costs 30 shields and 40 food.
Now the big question is how do we weight food, shields and gold and beakers. I weighted them all at 1:1:1:1. That can be reasonable, but it really depends on the relative scarcity. In a way that is more an opinion than a hard mathematical fact.
2) Does founding a Town give 7 Beakers immediately? Hadn't noticed that. Certainly in totally corrupt Towns there's only 1 BPT w/o Scientists.
A town in the desert generates:
-2 gtp worth of free unit support
-1 gtp from wealth
-3 beakers per turn from a scientist
-1 or more regular commerce
In that case of the early republic any addtional town nets at least 7 BPT. As most likely you are needing money to pay for unit support each additional free unit support can be translated into reserach, as can the money from wealth. Again the big question would be how we weight food, shields and gold and beakers.