scout1081 - I can answer your four questions.
As this is my first post on this forum, I will give some background on myself. I was in The Ontario Regiment from 1984-1990 and left with the rank of Sergeant. I have spent the last five years researching and writing the updated, official history of the Ontarios. "Fidelis et Paratus: A History of The Ontario Regiment (RCAC) 1866-2016" will be published this spring. There will be a book launch at the Colonel R.S. McLaughlin Armoury in Oshawa on April 30, 2016 from 1400 - 1600 hours.
1. Most of the crew members were Troopers. Corporal were sometimes a member of the crew (other than being the crew commander). The troop leader may have had a Corporal in his crew - I would have to do some digging.
2. Squadrons were commanded by Majors and troops were commanded by Lieutenants. From the nominal rolls that I've seen, the Ontarios had very few Second Lieutenants on strength. It would have been unusual for a Captain to command a troop.
3. One Thompson SMG was carried by the gunner in each vehicle. The other four crew members carried .38 Smith & Wesson pistols. The Thompsons were turned in for Stens when the Ontarios relocated to northwest Europe in March 1945.
4. Troops were numbered 1, 2, 3... 15.
You should find a copy of "3 Troop" by Captain (retired) Malcom Sullivan. He was in the Ontarios during the war and the book covers his experiences. It is very informative and entertaining.
The DND DHH website has some good documents on 1 CAB. Have a look here: http://www.cmp-cpm.forces.gc.ca/dhh-dhp/his/rep-rap/cmhqr-rqgmc-eng.asp