The answer why 80 or so years after Cyrus's decree, I agree, may be somewhat bothersome or hard to understand.
May I suggest this answer or possibility.
After Cyrus's decree, all of the Jews did not return to Judea. Daniel himself stayed back and took a high position in the Medes/Persian realm. In the book of Esther, we see that Esther and her uncle Mordecai as well as others remained in the Babylonian/Persian empire. Daniel might well have stayed for two reasons, at least as I can think of: his age being one, and his desire to be of help to his people in such a high position in the kingdom being the other.
Your assertion that 457 BC is the right date for the decree to start the 490-year period is correct. Cyrus's decree in Ezra 1 is only for the Jews to return to their homeland. Darius's decree is only a confirmation of Cyrus's. Some will take the record of Artaxerxes in Nehemiah as the starting point. Mathematically this does not fit.
444 BC minus 483 years to the time when the Messiah shows Himself will take you to 40 AD. (Remember you have to add 1 because there is no 0 BC or 0 AD. It goes from 1 BC to 1 AD). The only way to make 444 BC fit in well, from what I have found in my research, is to multiply 483 years (to when Messiah would show Himself), by 360 days, (the number of days in the Jewish year), and then divide by the number of days in the Julian and Gregorian year.
But this is incorrect for this reason: why would God give a time prophecy in which you use one calendar and then divide it by another that wasn't going to exist until almost 400 years later? One must remember, that God is dealing with His people and would use a measuring of time they would know.
Yet following this pattern of interpretation was plausible, and it would take you to 29 AD as the time when Christ came to John to be baptized. All scholars I have read seemed to recognize that Jesus was 30 when He began His ministry, coinciding with the priestly requirement of being 30 to start in the priestly service.
This would mean he was born in 2 BC which does not fit well with the Magi's visit, the escape to Egypt, and the death of Herod the Great. The account of the Magi's visit describes that when they came to visit they saw a young child, not an infant and they had followed the star for 2 years, hence Herod's order to kill all male infants up to 2 years old.
While there is some discrepancy on when Herod died, 4 or 2 BC, it fits in with the time that Jesus was born in 4 BC, went to Egypt in 2 BC, and later, Joseph having been informed by an angel that Herod was dead, went back settling in Nazareth.
The timetable of the 490 years beginning in 457 BC fits in with all the criteria, especially when you read the decrees of Cyrus and the two of Artaxerxes (in Ezra 7 and Nehemiah 1). The one in Ezra 7 is correct for this reason. It is the only one in which Artaxerxes gives orders for the Jews to set their own judges and magistrates and to govern by the Jewish laws. You won't find this in any other decree.
This would take you to full completion of the 490 years this way: 457 BC, the decree made, Jesus' baptism to begin His ministry in 27 AD, a covenant made to preach the gospel only to the Jews for the remaining week or 7 years, but the Messiah would be cut off, die, in the midst of the week in 30/31 AD, and the gospel still to be preached to the Jews, (as he said, "do not go but only to the lost sheep of Israel") until the death of Stephen in 34 AD.
At that time, in the book of Acts, it's recorded that a great persecution fell on the early church and many fled to parts of Syria. It wasn't long from this that we find the story of Peter going to a Gentile's home, preaching the gospel and their conversion, and recounting this to his Jewish brethren later in a council, that God has seen fit to take the gospel to the Gentiles.
And Paul's conversion was right after Stephen's death for he witnessed it, keeping at his feet the robes of those who took part in stoning. Then he received orders from the religious leaders to go after the church and made his way to Damascus, in Syria.
Hope this helps.