BettaFix does absolutely nothing, it's about as useless as a tiny net trying to catch a full grown Oscar fish. Aquarium salt should only be used in real sickness since it can have adverse effects if used too long and too often, the side effect being organ failure which means death. So only use it when you absolutely have to. Torn and ripped fins will heal given time and clean water, just keep the water clean and he will be fine. Bettas are amazing at regenerating their fins so don't worry, just take that stuff out of his tank.
It will heal, just do frequent water changes for him over the week, if he's in 3 gallons or smaller try to do water changes every other day around 30-50% to keep his water clean so it won't get infected. Good quality food helps as well as some Stress Coat water conditioner.