The contract will not be “at large”. What being “at large” means is that there is no completion date and no way for a completion date to be determined. That i9s clearly not the case here. The onus is on the Contractor to provide sufficient information to explain its claim for loss and expense and/or extension of time. To the extent that it does not the CA (architect) has an obligation to make a reasonable assessment using the information he has. In all likelihood this will be less than the contractor thinks is due and could easily be nothing.
If time were at large (and I repeat it is not in the case you have explained) then liquidated damages fall away as there is no specific completion date against which to assess them. The obligation on the contractor is to complete in a reasonable time and if he fails the employer may recover damages, those damages will have to be demonstrated to have been caused by the late completion. Al in all it gets very complicated and messy.