You didn't mention Romans 4:25 earlier, did you? If so, where did you do so? But this is what Paul wrote, in context:
I don't see where Paul wrote here that our redemption was "incomplete", until Jesus rose from the dead. Where did Paul write that here? Jesus Himself said "it is finished!" and there was an earthquake and the heavy temple curtain was torn in two from top to bottom, that separated the Holy of Holies from the rest of the temple.
But what else did Paul write? From Col. 2:
And from Romans 6:
Jesus took on Himself our sins, and nailed them to His cross. When He died, our sins "died' with Him. He therefore paid for them completely with His death.
Jesus also said in John 17:4--"I have brought you glory on earth by finishing the work you gave me to do." Jesus had not yet died on the cross and risen from the dead yet, He said he had finished or accomplished the work His Father gave Him to do. How is that? I think it is because Jesus knew He would do everything He came to earth to do; that He would suffer, die, and rise from the dead--even though those things were in the future.
But Jesus DID say from the cross "It is finished!" And He wasn't announcing the end of the Passover Seder meal. All Jews would have known when that was. They had been observing the Passover for over a thousand years.