Hi Becky,
I don't think you should worry about the Nova Scotia "marriage". It was most likely caused by Ancestry's handy pull-down list of place names that appears when you start typing in a place name. If you are using ancestry.com or .ca, it always suggests places in the US or Canada before those in the UK. The tree owner probably did not notice that she had chosen Halifax N.S as marriage place instead of Halifax, Yorkshire (same thing happened with Edith's birth place). The only wife listed for Arthur is the correct one, Edith Annie Alcock. The tree owner makes no claim that Arthur entered into a second "marriage" during his brief time in Canada.
It is annoying that you have not received a reply to your message, as it looks like the tree owner has many family photos and perhaps info to share. I suppose you noticed that she is a great granddaughter of Alfred Mothersole (1859-1940) who emigrated to Canada in 1906 (brother of Kate).
It is possible that your message was not sent to the tree owner. When you login to Ancestry, check "Messages" - "sent messages" to make sure. I sent a message last week and when I received no reply, checked, found that there was no record of it, even though I had done everything properly and the "message sent" box appeared after I clicked "send". I had to send a new message (which did get through).
hth,
Carmela