I saw the picture on the facebook page you linked to. Poor guy! That looks horrible. D: Bettafix is pretty bad, from what I've heard. Anything with the word "fix" in it, the members are usually against. If it's at all possible, I would upgrade him to something a bit bigger. The bowl is probably only a gallon, and cleaning only once a week isn't enough to keep the water as clean as it should be. Petsmart has some cheap Kritter Keepers of different sizes. I have one that's called a large sized KK, and it holds 3 gallons of water. Not saying you should get a 3 gallon, but I'm sure he'd appreciate the space. The medium sized one holds 2 gallons, I think. Also, I would get a heater of some kind (preferably adjustable, so you can set the temperature. The preset ones only heat to 78, or so they say) and a thermometer. The ideal temperature range for bettas is 78 to 84. Some bettas like it colder and some like it warmer, so it really depends on your betta. My boy betta lies 84, my girl likes 80 and my sister's boy likes 82. So it all varies, but it's generally all around the same range.
Clean, warm water (with the conditioner) should at least start helping a little bit. I've been treating my sister's sick fish and I've already seen a big improvement in just two days of having clean, warm water.
If you choose to keep him in the 1 gallon bowl, I think you should do water changes about every other day. I'm not sure what other members would recommend, but I would do 50% water changes every other day and a 100% at the end of the week. I'm pretty sure the other members might recommend more, but that's what I think could be done. It would at least be an improvement. :) For example, in my 3 gallon, I do 50% water changes on Monday and 100% water changes on Friday. I pick specific days, so it doesn't sneak up on me and I'm surprised that I have to do one. I even set calendar alerts in my phone to let me know when I need to do them. xD
I really do hope he gets better. That looks pretty bad. :(