RE: how to calculate dihedral angle?
Of course there is, but it may not be simple. There are several balancing of torques. For example, take the fin/rudder...
It is above the CG usually and so acts like half a wing. In sideslip, there would be a tendency to roll. A sideforce from the left may want to turn the nose to the left, but will cause a right roll. The effective angle of attack of the wing due to sideslip with dihedral is a simple formula,
angle of attack change = dihedral angle * sin ( yaw angle )
You would need to figure out the resulting rolling torque and balance it against the fin/rudder.
In a turn, there is also the effect of the outer wing travelling faster than the inner one. It's a small effect, but must be accounted for as well.