I started owning angelfish a couple of months ago and read everything i could about angelfish.
I suggest you search this forum on what i mentioned before and you will find out that many profession angelfish breeders agree with me especially on the temp. Most angelfish like warm water that is 80-82 degrees. If you don't have your water that high then it compromises the angelfish immune system which in turn gives you more problems.
You can also search for the mollies environment because i don't know for sure just think i have read it several places that mollies live in colder brackish water.
Salt will not hurt fish with scales but some do not like it as much as angels can handle. I suggest you look up as much information on fish forums about mollies as i do not know for sure what they like. Just because mollies don't act differently does not mean they are any more happier. What may seem happy to you may be different to someone else because they may have seen happier.
Your only using 1 teaspoon per 10 gallons? That is not effective. If you use salt you have to use it at higher concentrations for it to be effective. Let me find a couple of more sites some people have given me on salt and treatments. Here i found it:
Salt and Salt Treatments
Moving angelfish back and forth from different tanks is only going to stress that angelfish out. You should not be in a hurry to move the angel back to the other tank if there is something wrong with the angel. If the angel is mad at you about location well he will get over it with different types of food such as i suggested. If the angel is only stressed out and you move him back without giving it enough time to settle down in a new place then you are only adding to the problem.
I do 50-75% daily water changes with any fish that appears not well in any way including not eating as much. That does sound like a high water change but it is my preference because i want to do enough to get rid of most of the bad bacteria daily. Many people do not agree with this high of a water change on these boards but on other forums people tend to agree more so do what you will with my advice. I understand the risks of a high water change straight from the tap as the oxygen rises out of the water and may get in the fishes gills but i have yet to have a problem because of that. I have to warn you though that my water does not change from straight from the tap to a day after with aeration.
Also, let me mention the carbon factor. You do not need carbon in your filters unless you are removing meds. If you keep carbon in your filters daily and do not change them at least once a month then the toxins that the carbon collected from the water will spill back out and hurt your fish. Just wanted to let you know. On those forums i listed, it has a complete article devoted to just carbon in the filter.