1. A new heel plug could well solve all the problems at the foot of the mast plus a new bolt at the back of the track . As long as the plug right at the bottom of the mast sits on the bottom of the track you should be OK . When you take the mast pin out does the mast drop ?
2. As to rig tension the P&B tuning notes say that the leeward shroud should be just less than tight when going to windward .
Depending on the strength of the wind this will require a rig tension of between 300 and 400 lbs .