'Bad weather' is addressed by the appropriate compensation event, which is the subject of your recent similar post , 'NEC ECC: Compensation Event assumption' with a good answer from Glenn.
Any constraints on how the work is carried out and any allocation of risk is determined by the contract documentation, which you can't just change by including wording in a CE quotation. The assessed change to the Prices, therefore, should reflect these constraints and allocated risks.
If the quotation clarifies and defines the scope of the compensation event then that could be a different matter, especially where this is not clearly determined by the notification or instruction.
With regard to the 'material quantity' issue it possibly depends upon how the CE was presented in the Bill of Quantities under clause 63.13. That is whether the CE was simply included as an item or if the quantities were stated. If it was as 'measured' quantities then this could be a further CE, provided the tests under clause 60.4 apply.
Generally, however, an error in the estimation of a quantity in a quotation is, unfortunately, not a reason to revise or change a quotation, unless it was based upon a Project Manager's assumption, which would lead to a further CE.