Fascinating project. I hope all goes well. You discuss the pressure capability and possible deflection. What looks right often is right, but there is a free Finite element analysis program Z88 Aurora which will give you the answer in seconds. If you have produced the model for the 3D printer I think you could feed it straight in and check the stresses and deflections. Not at all difficult.
One question, you do not show any springs on the buttons, does the camera alone release the button or have you just not shown them?