well a pull off is when you fret a string on two different frets, pluck it, then a split second later, take off your first finger, changing the whole fretted note.
you just are sliding down, which is a totally different dynamic than pulling off.
as for harmonics, theres different types; natural and artificial.
some easy to hear natural harmonics are found over the 5th, 7th, and 12th frets. try barring your finger over the fret, barely touching the strings, and do a downstroke. it should get a very nice sounding tone.
artificial is probably what you are looking for in your genre of music. these are a bit harder to explain, so hang in there.
okay, so lets say you are fretting a G on the low E string (3rd fret) crank your distortion, and get on your bridge pup. okay, so do a monster bend with some vibrato- but instead of plucking the string like you normally would, choke up on the pick so that your thumb hits the string right after the pick does. that will cut the vibration of the string short, doing that "squeel" everyone wants. there will be different harmonics on different points on the string, so experiment. try for now just picking between the middle and neck pups.
they take practice, but hang in there. once you figure out how to do it, it'll come easy.
-Agile Guitars Enthusiast