What you say about a week is only true if not a leap year on the lunar-Solar calendar; when Easter can miss Passover by up to five weeks. And UNBIASED historical sources do attribute the move initally to Constantine. While most of your information is quite correct, the few inaccuracies or slanted presentations seem to be biased toward the RCC position. I am not sure if there is intent in that.
Amazing what you are willing to believe without actually studying the PRIMARY SOURCES.
You haven't read Bede's account, nor studied the history of the word Easter. Interestingly enough, you know who did? Tolkien. He has an entire book written on the subject of Celtic/Norse words coming into the English language. Easter is one of them.
Oh but Tolkien's a dark and biased Catholic who obviously would slant the history into his realm...except the fact that the Oxford dons who worked with him peer reviewed it and approved it. (By the way, Oxford isn't actually known for its pro-Catholic leanings in the 20th century).
Also, actually read Bede's account. He never mentions Eostre as a fertility goddess or that anything except for the "season" is known as Easter in...England...that's it. Not in Scotland, Ireland, or Wales. Just England.
As for Constantine moving the calendar...he actually didn't. He couldn't have, simply on his own. Since, the Christians would have to have been okay with it. Oh...and by the way, Christianity had only just been legalized. Christians wanted to celebrate and follow their holidays and festivals. You know what might have angered them? Messing with those holidays. In fact, we don't see Augustine, less than a hundred years after its legalization, nor any of the contemporary Christian leaders complaining or even supporting such a move. It simply doesn't exist. No primary sources.
What did happen under Constantine's reign was the Council of Nicea (which Constantine wasn't a part of), the finalizing of the Trinity Doctrine (which Constantine denied and was against until his death bed).
The only Christian holiday Constantine had anything to do with was Christmas. Most in the Greek and Latin world celebrated it in December, the date was rather different among them, but all in December. The Egyptian Church celebrated in late October, and the Asia Minor/Holy Land celebrated in January. Constantine demanded the Bishops decide a date. They chose December 25th. To appease Constantine since it was the day before Saturnalia (December 26th or modern day January 24th)? We don't know. Its not in the primary sources...at all. So the rest is speculation...
That's all this is speculations with a willing to believe our Christian forebears to be either dumb or sinister or just ignorant. I'm sorry, I just don't believe that.