Reply to changing tonearm on 1200 mk2 first time

i tested if my tone arm is in good condition by following the advice in the video below. it turns out that i've a bad tone arm because it does not move to the middle when i change the anti-skate from 3 to 0. prior to all of that, the stylus was skipping every time no matter what i set the counter weight. talking about counter weight, does anyone know what setting pro dj's put their counter weight on?

does anyone know a good site to get mk2 parts? and what i should order. thanks in advance.