Hey Kenny, thanks for your response yes I did end up doing that and it worked (yay). I reefed on the last floorboard hard and some of the fibreglass on the ground cracked
but I will likely be sanding down this whole floor and reinforcing many parts of it because there are cracks.
There were spaces for 1x2wood beams along the floor but they were under a thin layer of fibreglass which also had to be pulled up. Luckily the word and the fibreglass were silicone together instead of fibreglass, which made it slightly easier to take up.
I didn't take many pics of the process because I was working in the dark most days (dark at 5PM in Canada!). But essentially using that skill saw to cut a "matrix" along the ground then the crowbar and hammering it to pry up the floorboard worked.
I also found a hidden bonus crack in the floorboard! At night I used my work light
to shine from the bottom and all the thinner fibreglass and cracks show through, which is a great way to detect some sneaky cracks!