If I read the above it seems as if all the channels are busy. Is my assumption correct and if so what are my alternatives as we are not allowed to make use of 5Ghz in South Africa at this point in time.
You say you have one station as non-root but your configs show the bridges both at root, are you sure the configs. are correct?
How did you line the antennas up, by eyeballing it or some other way? The antennas you're using need correct alignment to function efficiently.
Is the 1.2km as the crow flies or as the car drives? If it's 1.2km straight I would suggest making the distance on the config as 1 not 2. Are you using miles or km? If the bridge is set for miles then 2 miles = approx. 3.23kms, that's a bit more than 1.2kms and may be affecting ping times.