Longer than OTL Borneo?
How big is Alaskan garrison?
Woud Canada be involved if Japan do not declare war to the UK?
Yes they would, in concert with the Americans, after the statute of Westminster, the Dominion had complete control of its foreign affairs. The declaration of war on Germany was delayed by a week to underline just that fact. Canada would in consultation with the US declare war on Japan.
One of the primary reasons for giving up the Anglo-Japanese agreement by the UK. Was opposition from Ottawa and Aust/N.Z. because of the increasing concerns in Washington regarding the Japanese. Australia and NZ would no doubt also make that same declaration.