Hello Nancy, When they say cable in crochet they are referring to front post dc or treble (FPDC, FPTR) and back post dc or trebles (BPDC,BPTR). I didn't read all of the instructions as I saw a discrepancy in the back post cable instruction and responded to that. I will say if you have a free pattern I have found several mistakes in those kinds of patterns. I have been told that they have not been tested.
You Wrote:
forward Cable (fwd cable): Skip each of the next 2 post sts, fptr around each of the next 2 post sts, working in front of the post sts just made, fptr around each skipped post st.
What they want you to do to get the cable stitch is to skip 2 post stitches and do your fptr stitch then go back to the 2 skipped stitches and do the fptr this give you a X ( like a twist) and that will give you the cable look as you continue up you rows.
You wrote:
Backward Cable (bwd cable): Skip each of the next 2 post sts, fptr around each of the next 2 post sts, working behind the post sts just made, fptr around each of the 2 skipped post sts
This instruction is not correct because your wrote Backward cable but the stitches say fptr and it should be back post tr.
To make cable stitches in pattern you make fptr, then bptr stitches. If the pattern is written wrong this might be why your back post treble doesn't look right.
I didn't read all of your post and I can't see the pattern clearly but let me know if this helped and if you are still stuck I will try to explain better.
Spoula
https://youtu.be/6KzAScFoJns