We agree on Cruz hitting Trump in return. If I was Cruz I would go nuclear on Trump. Throw every inconsistency, hypocrisy and cupidity at him with a generous helping of ridicule.
At the very least Cruz would get some practice. With good attacks he will forge an image of being strong an independent. The media will try to paint him as shrill or whatever, but a good attack will work if he sticks with it (doubles down the way Trump does, etc)