It doesn't really matter what the Contractor claiming - it is about what the contract says. The fact they took so long to do the quote does not change the wording of 63.1 that states that the quotation should be based upon forecast defined cost from the point at which the instruction to change the Works Information was given.
So the answer to your questions are:
1) no they don't have grounds to base it on actual cost, although they can if they want but the PM will then make their own assessment as to what would have been a reasonable cost of that event
2) they can close the argument by stating that they will make their own assessment for a reason stated in clause 64.1 (second bullet point) but also state they will ASSESS it in accordance with 63.1 (which is covered in answer 1 above).
3) I think these answers above should give the PM the relief they need, but other than that outside of the contract I could suggest yoga, pilates or may be just something alcoholic...
So the answer to your questions are:
1) no they don't have grounds to base it on actual cost, although they can if they want but the PM will then make their own assessment as to what would have been a reasonable cost of that event
2) they can close the argument by stating that they will make their own assessment for a reason stated in clause 64.1 (second bullet point) but also state they will ASSESS it in accordance with 63.1 (which is covered in answer 1 above).
3) I think these answers above should give the PM the relief they need, but other than that outside of the contract I could suggest yoga, pilates or may be just something alcoholic...