First of all about nothern site. I was thinking about that spot first of all too but rejected it. The city with just a pig will be weak for whole game especially considering plain hill silver consuming 2 food. We also doesnt seem to need silver that quick so we can wait to expand borders imho.
We have 2 alternatives:
First one shares rice, flood plain and mine from capital what is good for early game and acceptable for the later phase. Also it gets instantly connected to the cap so may be we could plant it as #3?
Second one gets the same resources as yours but also a sheep. This is not great site but normal as #5-#6 when we will be able to conver forests into development.
About southern cities.
I agree that having a city connected to cap is one of the most important goals because it gives 2 commerce at least. But my considerations were based on the following assumptions:
1) we will have 2 settlers with just 1 worker so working fish seems to be the most relevant choice. Being dependant to worker force makes any location less attractive. The first imporvement we will make will be cooper
2) we want some strong coastal cities
3) I know that we cant plant cities having everything we want in the first circle but what I like to do is to make #3 open some extra tiles for #4, #4 for #5 and so on.
When I plant on my #3 spot I let #4 to use sheep instantly. I think we will be not ready to use sheep with #3 by itself because no hunting and lack of workers but for #4 it can be right in time. #4 does not get gems instantly but after it expands borders. Not perfect but I dont see how we can connect it better and quicker.
Your 3b spot can be very strong for late game but it has nothing besides 4-food tiles for early game what is not good. Also it is worker-dependant. Rice is not really better than flood plain.
I was choosing between green hill and yellow hill, to 1 or to 2 from sheep. Yellow hill is better to plant but it doesnt have fish in first circle and also has much less coasts for Colossus. OTOH green hill placement has much less base production. So I want to hear your opinion about those rwo. 1 road tile will connect them to capital if I understand mechanics right.