Ok I don't understand? What happened with the heater that gave all your fish Ich? Ich is a parasite, I don't know how you can blame a heater?
The best stretch I can think of is that the heater failed, and that stressed out your fish, which lowered their immune systems and the ability to fight off the parasite.
Ich is common in fish, and most healthy fish can get it and not die. Weak fish are the ones you need to worry about.
Without knowing your circumstances, or your fish, the best I can recommend is buying a clean tote big enough to house all your fish, then add a heater, and hang on back skimmer. Treat the fish as needed, and leave them alone. Just make sure their temp is good, they have plenty of oxygen in the water, and do water changes as needed.
Give it six weeks before putting the fish back in the tank. The parasites living in the tank should have past their gestational period and died off already.
I'm sorry that you are battling Ich, the best I can tell you is that it could be much worse. I watched amylodonium (spelling is probably wrong) rip through 20 fish years ago. That was a load of $$$ down the drain

It came in on a emperor angle and I didn't catch it because it is black and so are the angels... I didn't do a separate quarantine and had them all together. by time I realized it, it was too late. All the fish were covered and dying left and right.
Fish can easily bounce back from Ich, you just need to give them a fighting chance. Time is of the essence here. If you don't have the money for a hob skimmer, just use a bubbler and an airstone to keep oxygen in the water. Totes are a lot cheaper than glass tanks, and better. Fish can't see out of them, and that helps reduce stress.
Best of luck, and keep us up to date...