Hello befree,
I've paddled sections of what you describe, from north of Choiceland to the White Fox bridge. And I've considered doing something akin to what you describe.
For a description of a portion of the river, see
http://www.wildpaddler.com/river_creeks/river_creeks.htm#torchriverAs you mention, running the Torch is water level dependant. Call the Sask Watershed Authority and get information directly from them. The Torch is regulated by the control structure at Candle Lake.
The Torch is a deceptively LONG river. Doing a quick measuring on google earth, I get 211 km. You can probably double that number because I didn't follow ANY of the meanders! Note also the Torch never reaches Tobin Lake. Rather, it follows the lake for some distance then joins the Saskatchewan River a fair distance later.
I know others that have paddled a section closer to Candle Lake. I would expect that beaver dams could be expected, but perhaps at high water they are submerged. From what I understand, most of the river is fairly slow and there will be points where you travel many kilometers on the river to cover very little distance as the crow flies due to the meanders (not that it necessarily matters). I was just playing around in Google Earth and found one section that is 7km on the water, and 2km as the crow flies. However, the area upstream and downstream from the Love bridge is fun whitewater.
One fellow I know of that is fairly familiar with the Torch is Larry Gill. He can likely better advise you than me. Larry is in Choiceland so look him up. Or PM/e-mail (see the buttons below) me and I can get you his e-mail address.
From Mark's web site (the fun section):

For maps, the best will be the topographic ones. You can buy the printed maps at a
SERM office, Eb's, Canada West Paddle Sports, etc. Or, you can download them at
http://www.geogratis.ca/geogratis/en/index.html (I take the files to Mondrian for printing).
Cheers,
Bryan