That is the arm rest and the easiest to fix, the vendor should be able to adjust that easily. A couple of things to check - when you release the arm rest does the arm rest lever slowly go down under its own weight or does it need a little pressure, if the latter can you feel any resistance. Does the arm rest go down slowly or fast, if fast then the damper fluid needs topping up.
Also, not sure what is going on with the anti skate weight, usually the weight is on fishing line / nylon type thread (Edit - looks like the twin is that supplied so OK) and definitely needs to be running over the wire frame in front of it, the position along the graduated bar give you the approx. anti skate setting (less towards the arm, more towards the turntable). The antiskate acts to pull the arm away from the centre of the record.
Hope this helps.