Next time you replace cables, give thought to using a standard bridle cable that runs form one brake arm to the other. What you are running now is the factory setup on very cheap bikes. They can be set up properly and apparently have reached that state, but they can be a royal PITA and if anything changes so you want to play with the bridle lengths and other setup issues, you are very limited.

To do this you will need both the wire bridle and the yoke fitting (the Tectro triangle on the OP's bike or a more simple bent aluminum triangle with a singe bolt for the primary brake cable).

Ben