Is the tug sprung or one you just pull down into position on the chain and then tighten the QR?
If the latter then just take up the slack in the chain, do up the QR and turn the cranks. You will feel if the chain is too tight as you turn. In my experience, those type of tugs dont stay tight enough to keep the chain over tight any way so you cant really go wrong. You want about half an inch of movement in the middle at the chains tight spot (meaning the naturally tightest spot when you turn the crank as chainrings are uneven and slightly off centred so they have a slight camming effect on the chain which will cause uneven tension)
As far as the thread on the QR, it should really be most of the way if not all of the way through the thread.
Pics?