Pool is heated to 82 degrees -- all disney pools are said to be at that.
In the past lifeguards are there during certain times but I have seen people in it swimming at 6am and as late as midnight. Not sure what the official hours are. Lifeguards were there from about 10am until around 6pm. Slide is closed when lifeguards are gone. Sorry can't be of more help on the pool.
Not sure about the spa time although there isn't a gate to close it off so might depend on how noisy you are ... perhaps someone knows for sure.