(A)
Peasycam has beginHUD
See Peasycam documentation
http://mrfeinberg.com/peasycam/reference/index.html
(B) make a invisible PGraphics pg that you draw your stuff on but each with a unique color that you store. When mouse is pressed use pg.get() to retrieve the color of the position. Look up the index of the item that has this color. It’s a picking technique.
(C) you can temporarily deactivate Peasycam, I think with cam.setActive(false);
Use lights(); - looks much better