Sounds like the belt on the alternator is slipping.
Your headlights may not dim because you don't have dimmer lights. Dimmer lights can blow and leave you with just the high beams.
no
Check the light dimmer switch to see if the lights go dimmer or they stay at the same brightness. It sounds like the dimmer switch is either stuck or bad.
It would go to the dimmer that controls the brightness of the dash lights.
Yes
Yes.
A "dimmer" switch will change the brightness of lights.
sounds like you need a new dimmer switch, or there is a loose wire
a dimmer
The dimmers control the intensity of the lights.
Yes it can.
As many as the watts or current the dimmer specs say it will control - less 10 percent