@paralel: some typewriters (and maybe printers also) used thermal transfer that is similar but with a ribbon and prints on normal paper. Silent and durable (but ribbons are expensive and there is a very annoying confidentiality issue). I think canon used this technology in the end of 198x years.
it could be many things:
_a power supply problem (12v too low in your Apple II+, the printer does not have a separate power supply)
_ on the 3rd photo there is a crack on a resistor network (middle right of the image).
many aging printer issues are with rubber drums that may just disappear...
to me the most obvious difference in text is the small C of Apple IIc (smaller capital bold for Irish label and lowercase bold for US). Space between the 2 I is also different.
It seems more a "Sans serif" early font than an arial (or maybe an original postscript helvetica)
all mouse handling is done in the COP chip on the IO-board, but it might just fail because of a bad connector on the motherboard.
if mouse position is good but button fails you can have one port of the cop bad but most probably it's just a contact problem, check cop support (it's not far from...
the pads from the ebay listing do not have the rigid top discs, so they must be glued to original discs (that can remain in place in the keyboard). It is the same method I used weeks ago.
it seems there is a 800k floppy (but maybe faulty) on ebay. I also have one (from an incomplete MacII I think) but untested and shipping will be far too expensive. Maybe a floppy emu would be a better option if you want to test many OS? you will also need the correct 2732 (io)rom (keep or dump...
the material should not be conductive on surface because some pads have a very thin track in the middle that must not be short (otherwise there are unexpected results like random keypress, I had this problem with my 1st version of aluminium+tape pads that were still conductive on the edge)...
fixing the keyboard takes time but it does not always take much money.
But you have to find the good material
My rebuild is here (in french but with photos):
http://www.silicium.org/forum/viewtopic.php?f=8&t=25619&hilit=lisa&start=60
for just a quick test you can directly type on...
cpu rom 3a needs video rom of the screen kit to display properly. A lisa can start with a rom mismatch but displays dots at (not really) random places instead of images.