in the past with bad ich, I try and get the tank temp up to about 84/85 or so. use salt and I used to use a half dose of a standard ich medicine too. in other words, I used the 'heat salt' cure but with a half dose of meds too. always seemed to work well.
you need the get the tank temp up there to get it off your fish quickly so the meds can kill the parasite when it is in the free swimming stage. high temps get the parasite into this stage fast.
good luck