You did a good job.
1. You can copy/past (CTRL+D) the camera you want to lock. It won't be locked, but at least you'll have a copy to keep if you screw up the second camera. Switch by attaching it to the render shader and click on the button under the preview 'use current camera', if you want to use it again.
2. It's leaking through the walls. With Path trace that won't be the case. You won't necessarily need lights to light up the paper windows. In the object itself you can use illumination (luminosity) of those particular parts. You won't have the leakage then. If you want a bit of fake lighting differences between windows or parts of windows, use a small scale power fractal into the illumination input, if needed feed it through a transform shader set to world position. If you save the dojo as tgo, and place it elsewhere, you won't have to relocate lights either, so it's much handier.