outhouse
Atheistically
The truth is that Thomas is dated to 125AD
That's not in any way, any kind of certainty. Some date it early, some date it a little later. I think your guess is fairly fine and only disagree with the certainty.
Both Osiris and Mithra had fathers who were Sun Gods.
Here your reaching.
Mithras may have depended solely on Christian text.
Osiris has no connection to Christianity what so ever, don't even go there. I know all he players personally.
The material most plagiarized was the OT text that already had these concepts.
The other plagiarized idea was the Emperor who was "son of god" first and the unknown NT authors used this as their SOURCE for "son of god" not any other religious concept.