Ok so I did what I could to see what the crack is as all my carpets and soundproofing is still out.
Firstly, if you go down the nut and bolt trick to reuse the bracket then i'd use something like this, possibly get it welded on if you know someone..

There's no clearance between the bracket and the floor for a normal bolt.
Secondly, as far as being able to replace the two studs with bolts should they sheer, i'd say good luck with that. Looks like they are welded in studs with no access unless you cut the floor. Sadly these studs are in a place where the floor splits into 2 skins leading up to the bulkhead. There is a grommit hole in the interior floor skin by the heater matrix area as the floor ramps up to the bulk head, I can clearly see the second skin.

My advice, soak the sh*t out of the nuts with WD overnight and be very gentle with them when trying to undo.