Ordinary Glue and Varnish for blade

First of all,

1. Table tennis glue is basically Rubber Cement so that is definitely usable as a TT glue alternative.  Personally, I use JOOLA ZOOM glue when I don't speed glue my rubbers.

2. The chipping you describe is when the rubber is peeled from the wood blade and some of the wood strands from the blade peel off with the glue.  It happens but isn't common if you take the rubber off with care(removing it in a horizontal motion instead of vertically).  Personally, I haven't tried hairspray but I've heard it works and I intend to try it.  Wood varnish is a good investment if you can find it in a small can(usually $5 or less).

3. I would have to say no, but there is no conclusive evidence that sealing a blade changes the blades characteristics drastically.  Although, I am not sure as I sealed my blades when I got them with a wood varnish.  There is a definite chance as wood varnish is harder than the wood itself but from what I've read and heard, it should have little effect on the playing abilities of the blade.

doraemon, here's a good guide to changing your own rubber.

http://www.masatenisi.org/english/rubberchg.htm

instead of using an exacto knife, many prefer a sharp pair of scissors(i know i do).

According to my experience, the best way in applying wood varnish is to put some on a rag and wipe it on the surface of the blade, in the same direction of the wood grain. One coat will give a very minimum coating. Then I wait at least one day, and if considered not enough, I apply the second coat.