My room lights' brightness pulses when I turn on my toaster oven
I've been in my attic and saw that some of the wires have been chewed
  bare by mice.


Whether this is the cause of the dimming or not, you need to immediately get an exterminator to rid your home of the mice problem and an electrician to assess and correct the damage.  Bare/exposed conductors is an exceedingly dangerous condition that cannot wait.