What are the elements needed in order to conduct a successful compliance review of a 6 month extension using a 52.217-8 for a contract over $3 Million?
“Compliance Review” is a term of art used by many organizations to ensure they are complying with FAR 1.602-1(b) “No contract shall be entered into unless the contracting officer... clearances and approvals, have been met.” The DFARS adds the term “Peer Reviews” at DFARS 201.170. You mention “over $3 million” but not by how much; but I will assume you are not even close to the dollar thresholds for peer reviews found in the DFARS.
Outside of peer reviews, and in most other instances, the FAR and DFARS only provide general guidance on when contract actions require review and approval before an action can be taken. It is left to the service component FAR supplements and/or organizational policy to provide guidance on dollar thresholds and specific procedures to follow.
In your case, AFARS 5101.602-2-90 and AFARS Appendix CC provides some overarching guidance but not to the specificity you desire. My advice is to ask your Contracting chain of command if there are dollar thresholds and procedures (i.e. checklists) you must follow before you can execute the modification to extend the services on your contract IAW FAR 52.217-8.
In general, you must follow all the requirements at FAR 17.207, DFARS 217.207 and AFARS 5117.207 before exercising the option.
That said, the Army used to have some unique policy regarding the use of 52.217-8 and ensuring it was evaluated during the original source selection to reserve the right to exercise the option unilaterally. I used to have a copy but couldn’t locate it, nor did an internet search locate it. You may want to read this interesting article from the Office of the Deputy Assistant Secretary of the Army for Procurement from July 2020.