My memory was off on Self correction by amendment, you can't correct in-service by retro-active amendment to conform to operation, it's you can amend hardship retro active to conform to plan's operation, and only if it was primarily for NHCEs who were affected.
So in this case the only "correct" way to fix is through VCP.
Now if the client finds the resolutions he adopted in December 2022 terminating the Plan in December 2022 and gives them to you, I'll leave it up to you whether you want to walk away from the plan or play audit roulette.
As for the failure to get Spousal consent, the fix is to get Spousal consent. If the spouse can't or won't consent the Plan is responsible for paying the spousal benefit.