I see...well I guess there will always be this difference in the shape of the cross between the different christians...but I guess it dosen't matter much to them.
The point about their being witnesses or not is still confusing. According to Matthew 26:56 the disciples fled, and I think its pretty clear. Were there other people witnessing this in that case?
None that wrote about the event. There were the Romans who crucified Jesus. The would have been present, but wouldn't have wasted time writing about it as Jesus was just one more Jew that they crucified. There may have been other condemned criminals who were also crucified with Jesus, but they obviously would not have wrote anything. And then there may have been a couple of people who passed by (probably not many if any since we are talking about it being Passover, and most Jews who were coming to Jerusalem for the event would have been there for about a week already) and they wouldn't have paid too much attention as they would have most likely been familiar with the sight.
So no, there were no one witnessing this that reported it. There were some witnesses, as explained above (at the very least, the people who crucified him), but they wouldn't have cared enough to write anything about it as it was just one more Jew that was being crucified.
We have no eyewitness accounts to this event. There is not a single one that we know of.
As for the difference in the cross shape, that really is not a major problem. The vast majority see the cross as it historically would have been, in the shape of a T.