Almost every time I watch a Youtube video dealing with knife heat treating these days I want to weep for the state of knowledge in our craft, however, the charcoal thing isn’t that bad. In fact, coal or charcoal can do a pretty darn nice job with a steel like 1084. Make a quick tunnel over the fire by stacking a couple of firebrick over a couple set on edge, then heat the fire until you have a nice blue flame coming out of either end of the tunnel and you will not only have some pretty good heat control, you will also have a nice reducing atmosphere that will keep your blade fairly clean.
Heat that canola to 130F and it will give better performance. Heat the blade to nonmagnetic, (but keep practicing until you can recognize the proper color of decalescence and it can be even better) then quench. Get it into the kitchen oven, set from 350F to 400F, right away to avoid possible cracking or warping.