the white is typically dried coolant. but if you mixed two incompatible (hard to do now as they are "safe" if newer of either type).. then they will start to harden inside, and be less efficient and thick.

the hose i think you are referring to is the heater hose that runs around the block, also feeds the heater core. not sure of the part number or name, but if that is it, you should consider replacing if possible.

the start should be swapped out from underneath?