I'm pretty sure it's recommended you slowly raise the temperature up to about 84 to help with clearing up ich. I've never dealt with it before, so I would suggest you ask darkmoon or OFL.
This is from darkmoons thread on diseases.
•Symptoms: Betta has white dots (looks like he was sprinkled with salt) all over his body and head, even eyes. Lethargic, No appetite, Clamped Fins, Might dart and scratching against decor
•Treatment: You can treat Ick either conservatively or with medication. Ick is a parasite. Because ick is contagious, it is preferable to treat the whole tank when one fish is found to have it. Ick is temperature sensitive: Leave your betta in the community tank and raise temperature to 85 F. Then you can choose to treat with salt or medication. Conservative: Add 1 tsp/gal Aquarium Salt 3 times, 12 hours apart so that you end up with 3 times the normal concentration. Perform daily 100% water changes to remove fallen parasites before they can reproduce. Replace the water with the right amount of salt. Do not continue this treatment for more than 14 days. If it fails or you do not want to use salt, treat with Jungle’s Parasite Clear, API Super Ick Cure, or Kordon Rid Ich Plus. If your betta lives in a jar/bowl, then it can be difficult to heat the water. There are heaters for smaller containers, but you can also float the quarantine container in a larger heated tank during treatment. Do a full water change every day and add an appropriate amount of medication to the water.
•Alternative Treatment: Personally, I have not found Ick medications very effective. I prefer to use PP to treat all external parasites. In the past, I have used 3 or 4 different ick medications unsuccessfully, and every time I resort to PP which works like a charm. Do lots of research before using PP as it is a more dangerous chemical than most.
The last ich spot vanished today. He has a few slightly whitish scales, but I'm not too concerned about those because they don't look like any disease, they're fading too, and he's getting even more active and friendly.
Just make sure and keep up the treatment for a few days more. I know you said you would but I wanted to reinforce it. Ich cysts break open and the parasite drops into your tank gravel. Once it's off the fish, you wanna keep up the salt and heat to kill it or it will just re-infect. I'm glad he's on the road to recovery. :D
I'm keeping up with it, of course. I also removed all the gravel that was in there when he first got ill, which has been washed in hot water and a bit of vinegar and left to dry out completely, and between water changes I'm washing the tank out in hot still-chlorinated tap water. It's looking positive so far ^^