You are definitely a worker, to the extent not often seen these days. By chance, did you (or your parents) emigrate to the U.S. from Europe?
Had I caught this thread earlier, I would have suggested you just fill all of the voids with what's called "flowable fill." It's just a weak concrete mix (3 or 4 sack) with a few additives to keep the rock suspended. You would have paid dearly for the small load charge, but it would have saved you a lot of work. You might consider tying the new pour to the existing step concrete by also utilizing the existing stub rebar to the right of the longer bar (you mentioned earlier). Straighten it out by bending with a length of pipe (grunt bar) over it, then splice a longer rebar to it with doubled tie wire. Some vigorous wire-brushing of both bars would also be in order, to improve the bond with your new concrete.