It is true that the Jews, Gods chosen people, are still waiting for their Messiah. However, not recognizing their own Messiah is part of Gods plan (Romans 11:25-27) that allows everyone else be saved (Joel 2:32; Romans 10:13). The Bible clearly states that those who are first will be last (Matthew 19:30 and 20:16, Mark 10:31, and Luke 13:30). The Jews were the first of Gods people, but they are kept unaware of their own Messiah until everyone on the earth hears about Jesus Christ. This is good news, since everyone gets a chance to accept the Messiah as their Savior and go to heaven. Once that happens, the remaining followers of Judaism will realize that Jesus was the Messiah. At that time, Jesus will return to the earth, bringing those who accept Him as their Savior to heaven. Those who do not accept Him will face God in judgment and be cast into the lake of fire (hell).
Why should anyone trust in Christianity over Islam, Buddhism, Mormonism, or anything else? It is because there are absolute truths. Only in Christianity are there accurately fulfilled prophecies of a coming Messiah. Only in Christianity do we have the extremely accurate transmission of the eyewitness documents (gospels), so we can trust what was originally written. Only in Christianity do we have the person of Christ who claimed to be God, performed many miracles to prove His claim of divinity, who died and rose from the dead, and who said that He alone was the Way, the Truth, and the Life (John 14:6). All this adds to the legitimacy and credibility of Christianity above all other religions--all based on the person of Jesus. It could not be that Jesus is the only Truth, and other religions also be the truth.
Neither by the Wednesday theory, could Firstfruits occur on Sunday, though that would place it after a sabbath, because that again places the resurrection on Sunday, which extends past the 72 hour rule they wish to adhere so rigorously to (A Sunday resurrection would make it the fourth day after the crucifixion). Proposing a Wednesday crucifixion and Sunday Firstfruits means adding two days to the scenario and again denying that 16 Nisan is the resurrection day and day of Firstfruits, thus breaking the type-antitype pattern. Since Sunday cannot possibly be called "the third day" since Jesus' crucifixion and burial under the Wednesday crucifixion theory, and can't be 16 Nisan either, it must also be disqualified as the day of Firstfruits.