Question about Pioneer MVH-330DAB

can be connected via chinch, the woofer usually has its own amplifier and only needs chinch and supply

Can send you a picture of the back of the unit, or you can check it out on Google (MVH-330DAB - pictures).

Yes, but only available as a preamplifier output (chinch), i.e. with additional power amplifier for rear speakers or subwoofer.

I don't know, but I just have problems with the volume control.
It hardly reacts and sometimes nothing reacts at all.

I don't know, I have a radio built into the tractor because of hands-free operation with a mobile phone.