I'm very much a beginner to parkour and freerunning, but this is one I can do. I'm also, 6'2'' and 170 lbs, so i'm very close to the OPs body type.
As far as how many steps to take your first time, my advice would be this: do whatever feels more natural and comfortable to you.
I started with a 2 step and still prefer a 2 step simply because it feels more natural.
The main key to this trick is feeling comfortable and natural and just doing it. Thus, I do what works best for you now, and then work on certain adjustments later, you'll know if something doesn't feel right or if you want to switch it up.
Make sure you feel comfortable going backwards. I could do a wallflip before I could do a standing back tuck - but I felt completely comfortable with the idea of rotating backwards from other activities.
Also, this trick is high impact because of the extra height, so make sure you practice safely. For me personally, the "trick" itself was very easy. The landing, however, was much more difficult. Once you "get it," keep working on making your landings better and softer; landing on the balls of your feet, absorbing with your legs, and not leaning forward as to put unneccessarry pressure on the ankles. It's good that you are starting on pads. Once you get it there, work on landing properly on grass before moving to concrete. Because, even if you land on your feet, it will be painful if you are landing wrong.
You should be pushing up to wall, not just away from it. and the push should be on the balls of your feet, pushing up, not flat footed on the wall. You don't need too much speed - I can do it from a standstill, the run(jog) just helps with getting a higher jump and gets the blood moving.
Anyways, my advice, for this trick, is to do what feels most natural to you.
