You don't want the floats in series. Then they BOTH have to be up for anything to happen. Parallel, any one will set off the alarm. Keep the alarm system independent; do not connect it to the pumps, they need their OWN floats. cross-connecting them to the alarms could have unpredictable consequences.
Connect the alarm to it's own battery or to a DIFFERENT battery than the one that runs the bilge pumps. Otherwise if you have a leak the bilge pumps will run the battery down first, and then the alarm won't work when you need it.
The water flow could be coming from your accumulator if you have one, but it should stop after a minute or two.
If your water tanks are above the level of the taps they'll gravitate through the pump and out the tap, even with the pump off. I wouldn't worry about it, just close the taps. You probably have a valve somewhere to shut off the tank supply.
You STILL have to run your pump and use the water in the tanks from time to time; or after a few months it'll get pretty nasty.
To be honest, I think all you've accomplished is make a lot of extra work for yourself.
She's a tired old barge but she's paid for! http://s71.photobucket.com/alb...p;current=ef324993.pbw