Triple Sulfa is a good antibiotic so if it's an infection that should likely clear it. Since you've started it I would treat for a full week, following the dosing instructions on the back. I believe it is every 24hours?
The bottle of tablets says to add half a tablet every 3 days. Although at the fish shop the guy said to do a 50% water change on day 3 before adding the other half of tablet. Not sure who's advice to follow.
I also bought some of seachem's Prime - so that at least the fish wont be getting hurt by toxic ammonia etc while I cant do water changes and the filter is dying.
He's still doing pretty well - no change in activity and he's eaten a whole bunch of blood worm I got him today :). It's 3 hours later - he is still scavanging around on the gravel looking for more.
Although he has been puffing up his collar at me a lot more than usual - pretty much every time I come near the tank - which Ive been finding a bit odd - maybe he's not in a happy mood with not feeling well.
My Brothers Betta Had The Same Problems Sadly the fish Had Tuberculoses But it died the white spot was just the same as yours I took 6weeks after the spot for the fish to die you should go get lots of help feed it bloodworms it makes the spot smaller i also read that and if it does not go down it will die in about 4weeks but it might survive lets hope and have faith in god that it will live ok I'm sorry for you and your fish