Your ambient temperatures are way too low. They should be at 80 degrees with a hot spot of 90. As for the heat probe, it should be inside the tank, under the substrate on the glass. For the ambient temp probe, place it on the other side of the tank, since you'll want to know about the coolest part of the tank. Make sure you have about 50% humidity in there as well. If you have a screen top and it's not covered, I'd recommend putting some aluminum foil over 90% of it to help keep in heat and humidity. A CHE or heat lamp will suck the humidity out like you wouldn't believe, so if that's what you need to get to keep the heat up in the tank, make sure you keep track of the humidity levels and mist once or twice a day to keep them up.
If you want to put in branches or things like that, it's totally up to you. He might use them, he might not. As long as you have two hides (one on the hotspot, one on the cool side) that's the only thing they really NEED. Ask yourself how much stuff do you want to clean every month?
As long as he eats on a regular 5 day schedule (how old is he? I'm assuming he's young), he should gain back the weight in no time.