Re-assurance

First off is it normal that when i put my car in drive it pushes the back end down and in reverse lifts it up i know there is a bit of torque to these cars so i figure checking wouldnt be a bad idea

Second i have an dc to ac converter and hooked to it a small amp i have set up (its properly wired trust me on this) yet when plugged in my cars rpms will sometimes although rare drop to zero and kill my car now its only when plugged in it did it about 5 min ago and i unplugged it my car rolled about 5 feet and the rmps returned to normal. Any thoughts besides the alternator being weak i cant think of why it would cause this but even with a weak alternator i figure it shouldnt shut my car down

Wicked Fast Entertainment