Similarly, does it limit the extent to which a Contractor can ever be liable for missing a Key Date?
In answer to your first question, the answer is ‘No’ as this is one of the “excluded matters” in clause X18.4 - the second bullet point, so in the unamended form, there is no cap on delay damages if X7 is part of the contract.
To answer to your second question, the answer is ‘Yes’ , up to the limit stated in Contract Data Pt 1 for the Contractor’s total liability. However, the Contractor’s “total liability”, excludes “excluded matters” ! Or put another, if the Contractor was not liable for any other damages - apart from the four types listed in excluded matters - then the total liability for however many Key Dates they miss, does not exceed the total liability stated in CD pt1.