As Mark suggested you can order his military records from Library and Archives Canada. Be prepared for a long wait, it can take 6 months or more for the records. I've posted the page on "how to order military records" below.
Fill the request in with as much info as you know (like the info you supplied us above). If you don't know something, like unit, or Regimental Number do not worry about it. Fill in everything you can. LAC will contact you (when they are ready to search) and let you know the cost etc. The "geni package" gives you abbreviated records......I would order his ENTIRE record, it will cost more, but has much more info (everything in the file).
You will need something to confirm his death, a copy of the death certificate, a photo of the headstone, something that gives them some proof he has passed away more than 20 years (this is so you can have access to all his file)
I will search the various source I have to see if I can spot any other info that may help you I will post it on this site for you