All good questions many which were asked of Jack in the early days at his "fireside chat" presentations/seminars/pizza parties at several pinball shows.
Jack said point blank that JJP was set up as a company (I don't recall if a Corporation or LLC) with a formal BoD and succession plan. If, God fobid tragedy strikes, JJP would continue and all games would be built and delivered that were ordered. He mentioned that game development would continue as well. He further stated that money is not an issue. I recall something to the effect that even if pre-order money stopped coming in, he could easily build all paid for games*.
As for other revenue streams; I believe JJP sells shirts, hats, translights, backglasses, Invisiglass, prototype playfields neon signs and clocks as well.
* Since these early days, some of the media stories & interviews may have contradicted this.
All of that said in an attempt to help you, you should call Jack as he does pick up the phone himself or he will definitely call you back if you have to leave a message. Ask him your questions and voice any concerns you may have. He will answer you honestly.