The QP SHOWER facility (sorry i did not mean toilets!) as in most lounges is perfect for me. Noone really hears me.and they are very private. The procedure i do also.makes me sweaty so a shower after is ideal. Previously flying OWA i was allowed to use most member lounges. Now i can't. I believe this to be because of my FF bronze status. Maybe I'm wrong or out of touch.
I am sympathetic to your situation and personal needs, but I'd think someone using a sower room for over 45 minutes (you noted earlier the procedure takes 45 minutes, plus a showeer) is quite extreme use to tie up a shower room for when many pax would like use of one. I am NOT calling you selfish, as you have a medical need here you can't alter how long it takes, but it is a considerable amount of time.
On the question of lifetime status, remember folks QF only started counting from I think 1997ish? so we're only really talking say 20-21 years of accrued SC's.
Though OP did say many years of being Silver to Plat status - I'd have expeccted at least Lifetime Silver, not Bronze, but that's a searate issue.
I'd also agree most lounges the bathrooms are not significantly cleaner or more sterile than some in the terminal. I've been in some that I've prefered out in the terminal! LOL
I do think many have suggested good ideas via Priority Pass, or a discount QC membership. I'd also suggest many airports specially internationally, offer showers one can access for a few $$ fee (I'm thinking of places like Singapore here).
It may even be good to look at day rates for airport hotels (some you can rent by the hour or so - and yes that sounds very dodgy but I don't mean it that way
) as another alternative.
These are costs you will just have to factor into your future travel.