Minor Problems with my 1996 A4 2.8

i have been driving my audi for about 2 weeks now i recently got it onto the road and it has been having some minor problems. The ABS light is on and so is the brake light. i had done the brakes my self and there was so sensor removed in the process anyware i was wondering how can i turn them off because souldnt they both be off? the brake light sould go on when the pads have been depleted right? and also my check enginge light has recently gone off and it now constantly lit up. Could it be that my stub mount is shot and the engine has moved and cause it to set something off. And the heating screen has been shutting off along with the whole intire heat not for long it just flashes and it shuts off and goes right back on sometimes fast enough for the screen to just blink and the fans keep running. If someone could give me some advice it would be really helpfuf