I am a fan of the Kiwame resistors.
They are silicone covered and film, not solid carbon, so flammability is not a problem.
For the two in the power supply you can use 5 Watters for a buck more. A 470k bleeder will draw less then 1 watt so you will have a large margin of safety.
The bleeder should go after the second choke. Part of it’s purpose is to partially load the supply to improve regulation, not an issue with a SE amp.
Adding more bleeders is not a good idea for a few reasons.
First each one draws current and a further load to the supply. Unless you make them so large that they don’t do a very good job of draining the supply.
If your trying to make it safer. Well you can’t , you still have to check with a meter before you stick your hand in there.
Power supply’s are like guns that way, no matter how unload they are, they still go off if you point them at someone…John