Don't use pool pH kits. Wrong chemicals.
No blankets, too flammable. Flat white paint is good. Tarps not good. Mylar camping/emergency blankets from camping section of walmart are better.
Let soil dry out between waterings.
40'F is WAY too cold and that's one of your main problems. Don't let it get below 60'F or above 85'F ever.
Please read the link in my signature for a bunch of useful info.