1 50% and 1 100% water changes per week for 1g, need to raise the temp, they like the higher 70s to lower 80s and even though he may of been active prior, being in constant cold water does catch up to them and makes them sluggish.
Bettafix = bad.
Fungus guard.. unless you see fungus.. no need to use it, most likely more harm then good.
Stress coat is good to use.
You mentioned you wanted to get him on AQ salt regularly.. unless you are healing him, don't use it on any normal occasion - it will actually make him sick after a period of time. (healing him as in fin rot, etc)
And get a water dechlorinator, PH down is something you do only when trying to balance your PH, could be doing a lot more harm with that then anything else. That will stress out your fish big time, as well as not take out the ammonia and such.
Any more questions, OFL is very knowledgeable and where I got my info :)