First, where did you get the idea that she was traveling nine months pregnant?
The Bible does not say how far along she was only that she came to term while they were there.
The night they arrived or three months later. It does not say.
Next where did you get the idea that she went on a donkey? Once again, the Bible does not say.
When people try to disprove something and do not bother to read the original source documents which are freely available you should not toss their work aside lightly.
You should throw it, with great force. Preferable at their head.
Because camels came along later and there was a really, really, long waiting list for a Ford?
You should throw it, with great force. Preferable at their head.
When did joseph have to pay his taxes, did he pay his taxes and then decide Mary might not be able to make the trip back until after the baby was born?
I can not see traveling 80 miles even if she was only six or seven months pregnant, too many questions, I like Mathew better.