Printer: for this and other purposes I've found that the scale in the direction that the paper is rolling can be off. Try printing a 100mm x 100mm square and measuring it with calipers. The 'across' direction is usually much better. Maybe it isn't an issue as you seldom require 0.1mm accuracy over a long distance such as 100mm on a PCB.
I didn't catch the chemicals you were using.
FWIW at uni we were using NaOH 'tablets' dissolved in hot water for the developer - saturated solution i.e. keep adding NaOH until it doesn't dissolve anymore.
For the etching IIRC it was 1/3rd HCl, 1/3rd hydrogen proxide, and 1/3 rd water. These are from memory... some common concentration (10M ?) for the HCl and similar for hydrogen peroxide. In a home environment I would worry about how to dispose of the chemicals, especially the etching solution containing Cu.
Removing resist and coating: I've used steel wool to remove the resist and give the board a polish, then a wipe with alcohol, and then a coat of PRF202 clearcoat (you can solder through it) containing flux.
For drilling by hand I recall leaving just a small etched circle at the center of each hole. This acts similarly to a spot-drill and centers the drill to the hole.