Hello Wallybanger;
Been a lurker, on D.B. forums, since 2004 & never disposed to "chime-in" on any thread, never mind "Beach-Bar". Always thought: between what I don't know (which I'll learn from professionals, like P.F.I.) & what I already know, but which may not work for others--I'd nothing to contribute. That said, your situation, question(s) & plans triggered something for me & felt compelled to jump in.
MonkeyHatFork is quite right: Mandy once told me equalization (e.q.) is a huge hurdle for
many of P.F.I.'s (& others') students. This, around time I gave myself mild middle-ear barotrauma, stupidly looking "up" (i.e. down, near bottom-plate) on a drop, thereby stalling my e.q. & stopping me from hitting target depth, that day or for duration of whole clinic. :head
Go here:
Liquivision : Freediving : equalizing [usual blab: if this link doesn't work (if it's "dead" text) then cut-&-paste into your browser...]
then download & save copy of proffered "Frenzel-Fattah" document & work through it, concurrent with your fitness-"cramming".
Give special attention to mastering "tongue-block"! It's easy for some people to slide into a Frenzel-Valsalva hybrid e.q. style, "blowing" from diaphragm--rather than "squishing" air up & back with tongue. Trouble is: on Breath-Hold & upside-down, "Valsalva-like" e.q. stops working, for many folks, somewhere between -5 & -10 m.
There's a solid reason tongue-block step comes before "Mouth-fill"--a.k.a. "negative packing", or "grouper-call"--in Mr. Fattah's ".Doc". Latter skill is later a big deal, facilitating truly deep dives.
Once found my way to:
Apnea mania
You could navigate to: "Training Tips"->"Static on Land"-> "Static in Bed". That one exercise is a mild, entry-level Hypoxic* breath-hold training "table". * i.e. it will help your body get used to low O2 levels.
N.B.:
Don't go beyond that exercise, without buddy/supervisor around. People HAVE blacked-out & fallen down, sustaining injuries during "Apnea-training-walks", etc.
Good luck! Not everybody "nails" Intermediate P.F.I. certification right away....
-Lepus-Aquaticus