One thing that is also going to help you get there is to play with doing some basic cross over turns. This will use simple inclination to engage the side cut of your board and will result in large radius turns with relatively shallow edge angles. Keep shoulders and hips aligned with the board and simply tilt your body back and forth over your board from heel to toe. Allow these turns to complete by crossing the fall line with the board perpendicular before going into the new turn. Edge change should occurr shortly after crossing the fall line.
Right now, your turns are very open ended "S" turns and I would like to see you complete your turns by making consistent "C" shaped turns. Bleed off speed by allowing the board to actually steer uphill before going into the new turn. You will need to work at getting comfortable with leaning down hill to initiate the new turn.
The secret to the steeps id overcoming that feeling of "leaning down the hill" Mechanically the board works the same regardless of the pitch. You need to try to maintain that upside down letter T in order to keep weight on the front half of the board in order for the side cut to be effective at turning.
Above is a quote from Snowolf on another thread that I think could be helpful to you (it was invaluable to me!!). The most important thing is to be 100% comfortable with your riding on gentler terrain. If you're not confident down below, it will just get worse on the steeps. Are you solidly linking turns? That's extremely important. I have just begun to really concquer blacks, and that is by making big C's with strong edge hold. On the steeps you want to make sure your board makes it all the way back across the fall line while still maintaining your edge. This will help you bleed off speed, and stay in control. You'll also want to look at the terrain you're riding, e.g. moguls, bumps, etc. and pick your line as best you can.
Trying the steeps in powder will give you more mental confidence, like Leo said 90% psychological, in powder you know that even if you crash, it won't be that hard. But
riding in powder is also a different discipline than regular riding. You'll need to lean back and keep your nose up to not get stuck.
Main thing, don't pin yourself down to a timeframe for progression, every rider progresses individually at their own pace and comfort level. There really is no way to figure out how quickly you will concquer the fear, or progress, but you will. If you improve just a little bit every time, that is progress enough worth being proud of! Don't walk away from your trips saying "i didn't do this or that" instead walk away saying "wow, i did this differently than before
and it felt good"!!! Take some lessons and keep it up!