Indoor air quality

My house was built in the late 50's the air quality inside my house is pretty good. The only cause for concerns that we have is the walls probably have bad lead paint under them from when it was built as the new paint cracks and falls off sometimes in the weirdest places. Our basement floods in heavy downpours from an outside drain that backs up. We have a gas furnace and gas water heater so there's a chance always of possible carbon monoxide poisoning but we have a detector. In one of the bathrooms one of the fans to take out moisture doesn't work so well and so some mold is growing on the ceiling. Some measures we could take are to clean or replace the fan and clean the mold. In the whole house we could strip all of the previous paint down and then repaint.