There was no such title as "Pontiff" in Rome when Constantine called the Council of Nicaea. Bishop Sylvester did not attend, ostensibly because of his age and infirmity.
No. Emperor Constantine was baptized on his deathbed and his mother, St. Helena, was a pious Christian.
A legend is a legend is a legend. There is no historical record whatsoever which documents the so-called "conversion".
One more example of "retroactive history".
Read your history. Emperor Constantine died in 337 AD soon after he was baptized by bishop Eusebius of Nicomedia.
Absence of proof is not proof of absence. More than sufficient indirect evidence is available to have convinced the vast majority of historians, regardless of their individual religious backgrounds and biases.
By the way, what exactly is a "Biblical Eunuchtarian"?