Is there an alternative or modified version of EVM that we can require a contractor to use in managing their program?
As discussed with you over the telephone, the Earned Value Management (EVM) requirement is designed to be applied on efforts that are measurable or discrete. Since the nature of the work in your case is primarily level of effort, EVM may not be the most effective management tool. Another option may be to design a more appropriate contracting strategy. If your RFP has not yet been released, and if you are highly concerned with efficiency on the SETA contract, you may want to consider an incentive type contract. An incentive type contract could be helpful in ensuring more efficient outcomes in your case. Of course, it is a management decision on whether to use an incentive type contract or proceed with a FFP contract--a FFP contract is more typical for use on service contracts where the work is not measurable.
The applicability requirements for EVM can be found at: https://www.dau.edu/mdid/Pages/EVMSApplicationRequirements.aspx
Per DFARS Subpart 234.201, EVM is discouraged on FFP contracts of any dollar value. DFARS Subpart 234.201 can be found here: https://www.acq.osd.mil/dpap/dars/dfars/html/current/234_2.htm#234.201
See also the DoD Earned Value Management Implementation Guide (EVMIG) for discussion about EVM applicability for service contracts, time and materials contracts and contracts composed primarily of level of effort activity. The EVMIG can be found at: https://www.acq.osd.mil/evm/assets/docs/DOD%20EVMIG-01-18-2019.pdf