I think "Decision Point" probably refers to Point of No Alternate in the case of flights to (mainly) island airports where it would be impractical or not possible to carry diversion fuel, e.g. Europe to Bermuda etc. On these flights an island reserve is carried (say 2 hours + holding) and there will be a point along track beyond which it will not be possible to divert to another airport.
A "Reclearance Procedure" applies to a flight which cannot load enough fuel to fly to the desired destination with all the normal reserves. In this case, assuming all the rules are obeyed, the flight may be despatched to a different "destination" with normal reserves. At some point on the way to the nearer destination it may be possible to continue to the original destination and complete the flight as planned. Whether or not this is possible will depend on how the flight has progressed (fuelwise).
Hope this helps!