Bandit 112 transtube very little volume and distorted

SOURCE: I have a peavey bandit 112 transtube guitar

This has several vacuum tubes and those are suspect. Take a pencil and tap the glass of the smaller tubes to look for noise changes. You may have to take off the tube metal shield to do this.
If you have got 15 years of life from the tubes that is great. Also suspect are electrolytic filter caps.
If you are not electronically adept, take it in for repair.

SOURCE: Hi I have a Peavey

No the 'send' socket is to plug in an external effects unit (it may also be used to feed a slave amp) but it will not disconnect the loudspeaker

SOURCE: I'm trying to get a crunchy metal sound from my

Overdrive is the key to the crunchy metal sound. The only effect on that amp is reverb.
You may want to consider getting an overdrive pedal to get the sound you want.

SOURCE: I have a Peavey Bandit

Take it for repair immediately as there is something that is thermally sensitive and it may cause worse damage with continued use. The problem is LIKELY a broken solder joint. Depending on where it is, it could cause damage to the power amp portion. It OFTEN is at one of the leads to a volume control and those USUALLY don't cause damage, but one can't be sure till it is repaired. These broken joints oxidize and then eventually warm and punch through and the device starts working. You MIGHT want to try wiggling the controls to see if one brings the unit on immediately showing itself as the culprit.