The resistor selection thing has been discussed before in this thread as well as the T2 thread.
No time to research all this again for you, so i'm speaking in general.
The Xicon though rated for 350 volts tend to work well,
although in one case somebody posted a pic of one that had shorted to the ground plane of the pcb.
If you have doubts, stand them off ~1/16" so the resistor body is not touching the pcb.
Again, if you have doubts 1/2 watt wont hurt. They fit and the brown Dale ones (CM60?) work well.
KG also employs the method you mention about stringing resistors in series to divide down
the voltage they see when a practical one component alternative is not available.
Looks like your pcb is already populated so all this is prolly moot.
One concern that I have is which plastic shoulder washers have you used on the heatsinks.
Please list the part number that you ordered / used.
They had better be the deeper ones or you'll be seeing fireworks when you power your amp on.
The correct plastic shoulder washers are a bit oversize and require drilling out the metal transistor tab
hole a few thousands of an inch (I used a dremel rasp) or pressing it in under pressure if you are lucky.
This too has been previously discussed in depth.