IMO a board is not a good long-term solution. Out of a case, it leaves dangerous voltages exposed, and if after building it you put the board in a case ... well why not build it into a case to start with?
If you're not up to case-work - and it's not everybody's cup of tea - , then find a friend who is, or pay a local carpenter. THis is an amp you may well want to enjoy for a long time!
You can see pics of my build at
http://www.jet5.com/triode.php. If doing it again, I would make the case slightly bigger.
My tuppence worth (UK version of 2c)
2) Read the hum thread in this forum - several builders have reported success. It worked for me.
4) Yes. Multimeter between ground and voltage point.