In this case, the wastegate has a spring that's trying to open it all the time, unlike a pressure type where the spring is trying to close it all the time. You would need a tension type spring working in opposition to the existing built-in spring in order to make the wastegate close tighter.
On a side note, I have read somewhere here that shortening the rod (adjusting the nuts) to bring the control arm into a more parallel position with the exhaust clamp can help increase or stabilize boost.
Finally, to answer your last question, the control arm moves AWAY from the clamp to close. The valve inside the housing stops against the casting to seal like a regular household door rather than swinging through.
You can see it in this picture:
