Peavey Bravo 112 hums and has less poast gain volume

Turn your guitar away from the amp's speakers. The pickups on the guitar are feeding the amp's signal back into the amp creating a feedback loop, especially with the gain button on. Loud volumes cause this looping path between the amp speakers and guitar pickups. You may need to reduce amp volume also.

Most of the time amplifier hum is caused by the outlet that it's plugged into, maybe no ground or there's other appliances on the same circuit causing interference? And sometimes it's as simple as a little internal feedback, certain C notes on the Guitar cause distortion with tube amps, the best fix is a $100 power conditioner like made by Monster cables or others.... hope this helps?

Numerous possible issues with your description. I would start with the tubes, and check if not one or more has faulted.

yes, if you know what is the amp module check.

Sounds like a bad power supply filter cap...the buzz you're hearing is the 60 cycles hum that filter caps reduce or (hopefully) eliminate altogether. It may also be related to the tubes but finding the bad one will require some work. Any friends have this same amp? If so, try swapping one tube at a time and see if you get lucky. If this amp is new take it back ASAP as it is a manufacturing defect.

have you tried using a foot pedal? Are you sure it is switching (green light turns red, etc?). On the lead channel are you turning up the gain all the way and the volume down?

Tone is a hard thing for some to achieve. Kinda sounds like the amp isn't satisfactory to you as a player. I use an ADA MP-1 with a quadraverb GT and I can sound like Steve Vai with almost any amp. The pedals you mentioned should all sound pretty good with almost any amp. You kinda sound as if your amp sounds wimpy. ALSO, a good metal distortion is a combo of effects as well as tone(layering). The sound you may be expecting may be the sounds of 4 effects combos at a time through a line mixer making it all sound like one sound. I use rack stuff BECAUSE I can get the sounds that NO pedals can give. This also sounds like your knowledge of the equipment needs improvement. True tweaking of gear takes years to perfect, especially if you're a picky guitarist like myself.

The amp is doing what is called "motorboating". This is usually caused when the voltages to sensitive preamp stages are inadequately filtered or regulated and the sudden load of the output stages cause a dip in the voltages sent to the preamps which in turn vary the input to the output stages starting the cycle over. This will require electronic troubleshooting and if your not skilled in that, then it is NOT a DIY fix. What you are seeing is NOT normal, there is a defect.

Buy ONE new 12AX7 and try it in location V1 and if it doesn't help, try it in V2. This tube has TWO heaters in it and if one is intermittent that could cause your problem. The vibration MIGHT be "fixing" a briken heater after some time.
There are MANY components that could cause this, so you might have to take it in for repair if it isn't a simple tube problem. Since it works on the clean channel, V3 should be OK.

The preamp section has a problem. It could be anything in the preamp but is OFTEN the input jack itself. They take a lot of abuse.

Also the insert jack contacts that forward the preamp to the power amp if no external FX are used can go bad.

Additional things are circuit board cracks caused by rough handling and also controls that have had the knobs mashed in which can destroy the potentiometers they are connected to.