I cannot help you with specific route information. But on the question of the credential, there should be no difficulty using a single credential for the whole journey you are proposing. While some associations offer a credencial of their own design, provided they conform to the basic requirements established by the Pilgrim Office, they can be used on any route.
Others will be able to better describe the history of this, but a few years ago the Pilgrim Office established new rules about what needed to be included on the credencials, and who could supply them. I understand this was to stop a practice by tour companies in particular from profiting from the printing and distribution of their own credencials at somewhat higher prices than those provided by the cathedral and pilgrim associations, and to standardise the wording about the requirements, eg to collect two sellos a day in the last 100 km.
Recently, I walked the Camino do Tejo, the route from Lisbon to Fatima, using the credencial provided by a now defunct Portuguese pilgrim association. After Fatima, I walked from Tomar to Santiago on the CP, using a credencial from the Santiago Cathedral, intending to only 'claim' that as the distance that I had walked to Santiago. However, when I got to the Pilgrim Office, the person preparing my compostela and distance certificates seemed to know that there is no equivalent document provided at Fatima, and included the Camino do Tejo in the distance calculations, and recorded my departure point as Lisbon. This was despite the credencial I used not complying with the current rules from Santiago.
There will, no doubt, be many similar stories about walking with locally produced credencials, I suspect from the time before the Pilgrim Office established the current rules. Certainly I have a couple, but now I use a credencial from the pilgrim office or from one of the associations authorized. There will be a Canadian pilgrim association who provide on for you before departure if you wanted to have it with you on arrival.