Which foot does each of the backs step with first?
I had the 1b step with his left foot first. Covers more distance.
2b same thing.
3b  right foot towards the line for a banana path to the end.
4b  right foot so his outside foot is planted when he goes around the DE(if the de hits him he has more balance).  If he goes under the DE left foot for the same reason.

You are correct.  Don't change a thing.

I'd have the 1 back use whatever steps he needed to have his hips open to the ball as it gets there.

I didn't stress the actual steps to the backs unless I needed to. Meaning as long as they were hitting the hole and the spots at the required angles I didn't over complicate it. But sometimes the 1 back would come to far forward on his first steps causing him to hit the hole at too flat an angle, with the shoulders facing the sideline rather than the endzone. In that case, I would make sure he opened up with a flat step with his right foot first so that he could attack the hole at a more direct angle heading down the field rather than down the LOS.