I deleted most of the post since it was a bit long winded and not needed to be repeated.
You did not fail DIRF .. your instructors failed to help you succeed.
There is only ONE practice for diving.............. Diving.
Put your **** on, put the face thing on, put the feet things on, put the breathing thing in your mouth and get in the water. Go do 20-30 dives in your rig and make minor adjustments on each dive. You can dive in ANY gear and achieve good form.
Guess what -- with only diving since last June you cannot be perfect. Nor should you. Go dive and have some fun. It sounds like you are not having fun yet.
Get a nice mess of Ettoufe' then night before. Then pack a muffuletta and go do some dives. leave the puke-green Kool-Aide home.
The more you dissect what you are doing the harder it will be.