Any thoughts on the contradiction between John having Jesus as crucified on the eve of Passover and the other gospels on Passover itself?
This is a somewhat complicated question. There is no doubt that John tells us Jesus was crucified on the eve of the Passover. It was also the day before a Sabbath. The Jews had different Sabbaths (note the wording in Colossians 2:16 where he says "a" Sabbath, not "the" Sabbath, because there were different Sabbaths). There were the Saturday Sabbaths and other "Sabbaths" such as the Passover. This is the source of possible confusion.
The question is whether the Sabbath which came the next day was a Saturday Sabbath or the Passover Sabbath or both. I believe that all the evidence is unanimous that Jesus was crucufied on the day before the Passover. Matthew confirms this, as in Matthew 27:62 he says that the day after the crucifixion was the "one after Preparation Day" (ie preparation day for the Passover.
Some people use the wording to conclude that Jesus was crucified on a Thursday instead of a Friday. This is in principle possible because the Passover can fall on a Friday. In this case, the crucifixion would still be on the eve of the Passover and on the day before a Sabbath, but not a Saturday Sabbath.
Whether he was crucufied on Thursday or Friday is not important to Christianity. What is important for type/antitype purposes is that he was crucified on the eve of the Passover and that the dinner which was celebrated which we know as the Last Supper was the Jewis seder/preparation meal. I believe that this is solid and that the biblical writers are unanimous on this.
Whether the crucifixion was Thursday or Friday would determine for us the year Jesus was killed. Right now I am in China, and I am working from memory, but whether it was Thursday or Friday would determine if Jesus was crucified in AD 29 or 30. The year and the day of the week are not essential to Christianity and therefore the doubt about this is not important. However, the religiously important timing, which is the symbolic (and the real) relationship to the Passover and the Feast of Firstfruits is solid and all the gospel writers agree on the fact that Jesus was killed on the Preparation Day.
By the way, I suppose I am supposed to express my opinion about whether it was Thursday or Friday. I lean slightly toward Friday, but this is principally because of the strength of the tradition in the early church. The tradition goes far enough back in time that I am inclined to think it is very likely that the early church had it right. If this is true then I believe it implies Jesus was crucified in AD 30.