Awesome explination, thanks!! so I possible solution would be eliminate de diving that obligates me to hold the neck from diving, which will give me totally freedom fingering across the neck and I can achieve that changing the tuners or/and with a double strap or re positioning the bass by adding a straplock somewhere behind my bass. (?)
I have lightweight tuners & they make a real difference to neck dive - and tune way more smoothly than the original ones. The DuoStrap is just a relevatiion in comfort & stability for me but it might take you a couple of weeks messing with the adjustment to get it perfect. But the first and cheapest one is move that rear strap pin up 4” & that will help heaps. If money is an issue I’d go tuners & pin mod first as it will also move the nut closer to you and get your left wrist comfortable. But the DuoStrap should be on your shopping list when you can IMHO.
After that, start making that adjustment to your playing position to get the bass into a position that keeps your wrist and forearm nice and comfortable. And good luck - my playing is way better now simply because I’m no longer fighting my bass so there is a real benefit to getting these little things right - for you.