I use a heyco grip cord to waterproof where the cable meets the housing but I'm going from beneath because it needs a flat surface, not a curved one from the side.
I use silicon to seal the cap.
So, the curing silicone fumes don't do any harm? And, I know it doesn't adhere strongly to acrylic, but there shouldn't be any stress on it to keep it from sealing. I can't see any way to ever get back into the sensor housing once I seal it, whether with silicone or anything else, so is there a good reason not to use high viscosity acrylic cement to seal the lid on permanently? The solvent fumes? Remember it is threaded on too.