Nice milky way view there, Student.
If you want to stack, you really need to use full RAW. The Canon mRAW format is actually more like a JPEG than anything, a 4:2:2 encoding of Y (luminance) and Cb (blue/yellow channel) and Cr (red/green channel). It is 14-bit, but it is actually not even remotely "raw". Stacking non-raw images doesn't produce nearly the same kind of results as stacking true RAW images.
For stacking to be most effective, you also want to have fairly closely temperature matched "dark frames" (same exposure time, ISO, and temperature...within a few degrees), say 30 of them, as well as about 150 "bias frames" (same ISO, shortest possible exposure time like 1/4000th or 1/8000th...super easy to create, and the more you stack, the better they are to calibrate.)
Once you have some real RAW lights, and some darks and biases, then you can stack with DSS, and the process is largely automated. Export as a TIFF (WITHOUT applying modifications), and you can do some pretty amazing tweaking and stretching in photoshop.