What a pickle.
These jetted tubs need to be tested before installing them. A crack in a line most likely means there is a leak and the tub should not be used as a tub again until fixed.
The fix would be a tub removal, repairs, inspection and then re-installed. If the fittings that are cracked can be reached from the access panel that's great but what about the ones around the back side?
I hate spiders. Not because I'm scared but because here in North Vancouver they grow huge and in the early morning one scooting across the floor looks like a bigger bug or mouse. I hate mice.
When dealing with the repair company make sure that the tub is filled overnight to the overflow mark. It should hold easy 24-72 hours with no leaks. Once this is done I would say you have a repaired tub.
I would also run the system as well to make sure all pieces are working.
They make a chemical cleaner to clean the lines and this would be another good step.
As for spray foaming the underside be careful - spray foam can wreck havoic on those lines and piping - even cause a new leak if poorly done!!!
Good Luck. If you where in Vancouver I would try and convince you to rip it out, buy a nice ACO shower drain and turn that tub into a steam shower for two!!!