Coppersafe is bad stuff from what I've read elsewhere. Don't use it unless you absolutely have to. I didn't know this the first time I used it... :(
What I learned on the other fish-keeping site (not betta specific, just fish):
Copper is a toxin. It works to kill the parasites, but it is also killing your fish "just a little bit". The levels in coppersafe don't kill your fish immediately, but the copper can have prolonged negative health effects and may shorten their lifespan. Also, once you've had copper in your tank, it's in there, forever. You can never completely get rid of it. OFL was kind enough to give me that information. It gets down into the sealants and into the plants/ornaments.
Apparently, aquarists were using big sheets of copper just stuck down in tanks many years ago when someone realized it was great for killing and preventing diseases like Ich...then someone finally realized it was also harming/stressing the fish, and so the practice stopped. But, you still have products like coppersafe on the market.
I used it on my boy, and within a few days his fin tips started to get red streaks in them. At first I thought he had septicemia, and I thought that he'd probably die. I treated him for septicemia, bringing on more stress, and making the red streaks worse. I finally gave up, stopped treating, and he got better. Since then, I've noticed with all my fish with white on the edges of their fins, when they're stressed the red streaks reappear, so it's definitely related to water-quality, disease, and stress.
Later, I thought he had Ich again, so I re-treated in coppersafe, and within 12 hours the red streaks reappeared, stopped treatment (new water, new tank) and he was once again back to normal. (No ich, his color was just changing.)
I wouldn't use coppersafe. Most stores will take it back if you haven't opened it yet, and there are *lots* of Ich treatments out there that don't contain copper and work well.
I hope that was helpful to you, and please don't think that I'm blaming you or anything, I just wanted to pass on what I had learned/experienced from the same issue and hopefully save someone else the stress. :) I had the same thoughts, bought the same meds, and it was detrimental to my fish, so I've been where you are! :)
I hope your boy is well and happy again soon, and good luck to you!