Can we change a FFP contract without an EPA clause? If so, what regulatory citations allow overriding FAR 16.202-1? Can FAR 1.102 allow it?
No, you may not change the contract price structure of a Firm-FIxed Price after it has been awarded.
"Courts have interpreted the FAR to preclude adjustment or reimbursement for the value of fixed-price contracts. See Info. Sys. & Networks Corp. v. United States, 64 Fed. Cl. 599, 606 (2005)."
"“In a fixed price contract, if the final total costs of the agreed upon services exceed the contracted price, the contractor takes the loss; conversely, he can profit if the costs are lower than the contract price.” S & B/BIBB Hines PB 3 Joint Venture v. Progress Energy Florida, Inc., 365 F. App’x 202, 203 (11th Cir. 2010) (internal citations and quotations omitted). “A firm-fixed-price contract provides for a price that is not subject to any adjustment on the basis of the contractor’s cost experience in performing the contract. This contract type places upon the contractor maximum risk and full responsibility for all costs and resulting profit or loss.” Prime v. Post, Buckley, Schuh & Jernigan, Inc., No. 6:10-CV-1950-ORL-36, 2013 WL 4506357, at 9 (M.D. Fla. Aug. 23, 2013)."
This answer is based upon the information provided in the question and the question background.