Cool project!

I would not worry so much about the weight and focus on getting the stab 100% balanced. Planes that are bigger like this tend to have light wing loadings but allot of stress on the control surfaces. Even if you have lead in the nose the stab needs to be balanced.

I would go with 400oz servos since they are around the same price and pretty standard now. Make sure you use max mechanical advantage by using the inside holes on the servo. Go to dreamworks RC and you should be able to get a rod and some clamps for a servo horn.

On the tab I have worked on real ones and its a simple piano hinge. You should do the same on yours.