You have not said if any water got in the trunk at all. If it did then the central locking pump buried under the foam and under the trunk mat causes all sorts of problems when it gets wet.
Look for the obvious first, do not get swung away from the moisture problem and the damage it can cause.
The ABS and battery problems would be a real coincidence.
I don't know that water got in the trunk but i have a feeling you are right about this. The hubby is going to check as soon as he gets and chance and see i there is water in there. I'm betting you are right!
Thanks