Well I hope you're not drowning by now, but if it helps here it goes. Have you shut off the water valves behind your toilet and sink? Turn them to the right and it should stop the flow, if it is clear water.
You have a slumlord (as you obviously know), report them to the city housing department. Try to find a renters advocacy group in your area, they will help you navigate the landlord/tenant laws.
If you have any more issues with your place, please PM me. My mom is an architect/builder and I have grown up around building houses, I know how to fix the problems that come with them (ok, I can't tell you how to rewire the place, but I can tell you how to handle most everything else).