Perhaps you could publish a pdf of your book on CD. It certainly keeps your costs to a minimum. You could keep a list of the purchasers of your book and send them an e-mail supplement to handle new/updated information, or sell a revised second edition if it merits the effort.
The important thing is to get something out the door. We will all be at a great loss if something should happen that prevents you from passing your knowledge down to future generations. Sounds like you've got it 99.44% done and the last .56% could take forever to finish. As they say in the movie business "a movie is NEVER finished, just finally abandoned."
Bruce Barlow released his "Finely Focused" pdf CD without illustrations, then later added the illustrations and sent all of the early purchasers an "updated" version free of charge.
I look forward to the release of both the book and DVD.