rescued mistreated betta fish - help please

Question
I became physically ill looking at all the sick and dead fish and then saw this one, helpless little female, looking at me through her tiny, filthy cup - I couldn't just walk away from her. (at Walmart) I had no fish equipment at all - so I bought a small tank, (holds 1 gal)., betta flakes, stresscoat, a little silk plant and a little cave.

I've had her for 2 days now - I'm using bottled water.  Her color seems to have improved from a dull, greyish orange to redder. She had some cottony stuff on her, (fungus or Columnaris?) and a torn dorsal fin.

A couple of q.'s
- 1. Can I move her into the sunlight during the day, just for the natural light/warmth effect? (I live in the north - no risk of overheating, no draft there, either.)  Is it o.k. to very gently lift her tank and move her wherever I am - she really watches me!
2.  How many granules of salt per 1 gal. of water?  How many drops of Stresscoat?
3.  Should I do a total water change every 2 days - and rinse her gravel - everything? (with water at same temp. etc. as old water.)
or should I just do 25%. I read about the good bacteria needed, but then I read about doing total water changes and I'm not sure which is best.

Thank you for your great information in advance - I read a response you gave, and I can tell you care about fish/animals like I do.  Wish everyone did - it is deplorable and utterly inhumane the way these shops and suppliers continue to neglect these poor, helpless fish. (and the major pet stores are no different - dead fish there, too! - so upsetting.)
Thanks again for your help, Lynda!

Answer
Hi Marybeth,
Bless you heart for trying to save this little betta from a sure death.  These places should not be allowed to sell fish, as they know nothing about them, and most do not care.  Unfortunately there are no laws to help prevent this, and it just breaks my heart when I see these fish who are so clever in little cups, or polluted tanks.  The betta is a money making machine.  Most vendors do not care, so give you wrong information on how the betta should be kept.  They are there to sell their gadgets, and make lots of money on medication, and small unsuitable tanks that they sell for this fish.  The customer who gets so attached to this little fish, is quickly hurt, when the betta dies, and this could be avoided if only the vendor would tell the truth, know the truth, and care.  
Here is information on the betta, and how it should be kept:
A betta should be kept in a heated 5 gallon tank.  In his/her habitat, the betta may live in shallow water, but they have lots of room to swim.  When bringing home a betta, you put him in the same temperature water has he is in, then you heat his water in the tank with a heater (Thermostat) one degree every two days.  Never bring the temperature up too quickly as this would cause death.  They are tropical fish, and must be in 80-82 degree water.  They should have a silk plant, and some little toy they can go through.  Never put your betta in the sun.  This would cause your water to fluctuate.  It would get warm during the day, and colder during the night.  Fluctuating water is very bad for fish.  It must be stable.  Heating water with lamps is also unsuitable as the water would be warmer at the top, than the bottom.  Bettas do not like bright lights, and prefer the light of day.
Bettas kept in small tanks, vases, mirror tanks will get sick, and their lives are cut short.  A well kept betta will live up to 7 years.
Bettas must have varied diets to get all the vitamins they need.  Betta pellets, Betta flakes, Plankton flakes, Daphnia, Daphnia is very important as it helps with their digestive system, Bloodworms once a week as a treat, Mealworms, Glassworms, and Frozen Brine Shrimp.  One frozen cooked pea with the first layer removed, and cut into tiny pieces is a must, once a week.  On the day you choose to feed her the pea, feed her nothing else for the rest of the day.  This is so she can clean out her system, and avoid Swim Bladder Disease, to which the Betta is prone.
I do not expect you to go out and buy all of these foods, but little by little try to vary her menu.  Give her one food one day, a different food the next, and so on.  Be careful not to overfeed her.  Her tummy is the size of her eye, so we must be careful when feeding her.  Feed her 2-3 times a day.  Two pellets, or two flakes for one meal.
Since she is now in a one gallon tank, it would be best to try to buy her bigger with a heater.  If you cannot do this, change all of her water with a good water conditioner such as Stress Coat or AquaPlus.  There is also a conditioner made especially for bettas, and the dosage is written on the bottle.  You should use about 0.5ml for a one gallon tank if using any other conditioner.  Change her water every 3 days, and clean your gravel.  If you go with a 5 gallon tank, change all of her water every 6-7 days.  
If you want to cycle a tank, this may take anywhere from 4 weeks to 6 weeks.  A cycled tank means that you must have a filter.  Buy a used sponge, squeeze out the access water, and put it directly into your filter, and let your water run over it, adding water that has evaporated from your tank.  Once your water has cycled, this means, that you should have zero ammonia, zero nitrites, and nitrates should be low, you may add your betta to this tank.  After your tank as cycled you must change the water 25% every week, but you must have a cycled tank to do this.  When you clean your filter, always rinse the sponge in water your have removed from the tank, and never under tap water.  A sponge is full of good bacteria, and is good for a very long time, until it is old ragged, and falling apart.  You must change your carbon once a month.  The carbon may be rinsed under the tap until the water runs clear through it.  If you choose not to do this, then all the water should be changed once a week in a 5 gallon tank, more in a smaller tank.  This decision is up to you, and what your prefer.  One teaspoon of diluted aquarium salt to 5 gallons of water helps with stress, and parasites.
For now, put 1/4 teaspoon of diluted aquarium salt into your tank, and buy tetracycline.  Follow the directions on the package, and be careful not to overdose.  
If you need anymore information, please do not hesitate to write me.
I hope the little girl makes it.
Lynda