As far as the early church goes, look into the writings of Origen (c. 185) who believed and taught universal reconciliation. Jerome, who translated the scripture into Latin, is quoted as saying, "I know that most persons understand by the story of Nineveh and its king, the ultimate forgiveness of the devil and all rational creatures". Wow. And then I read about this quote in the Schaff Herzog Encyclopedia of Religous Knowledge, 1912, " In the first five or six centuries of Christianity there were six known theological schools, of which four were Universalist, one accepted conditional immortality, and one (Rome) taught endless punishment of the wicked."
I've read that it took a long time before those who believed in UR were called heretic. I read that Universal Reconciliation, though often believed, was taught to the spiritually mature while punishment was taught to the immature. Some of the quotes I found seem to bear that out.
I've written this before, but it bears repeating. When I first came to Ray's teaching all I really knew was that the old testament did not teach hell, that God is Love and Love never Fails, and that "every knee shall bow, every tongue confess Jesus as Lord". That really was it. And then I knew every verse you know that seems to teach hell. But it doesn't - it really doesn't.
It does teach a difference between the elect and the non elect. Jesus is talking to Jews who are about to be left out of the Promise. They thought they were all that, and they were about to find the promise excluding them who did not believe Him and going to the Gentiles . Weeping and gnashing of teeth is an expression that means Great Regret, and that's how all those who thought they were God's Chosen will feel when they are left out of His elect.
I hope you continue to let us know how your studying is going and what your questions are.