All of the answers are in th article.
Half dosing salt is not a good idea, and honestly neither is half dosing meds. ?One of the reasons I reccomend salt for sensative fish is that half dosing meds is not very successful, and therefore it's better to use a method that the fish can tolerate full dose. Salt really won't hurt too many fish short term. it does irritate them, but not significantly like meds.
Any gap in treatment is the same as starting over. if you leave the tank unprotected, any ich that hatches during that time can find a host and re-start the life cycle. This is another reason I don't like meds. Meds lose potency as they stay in your tank. So you dose the tank, the meds are real strong, by the time you put the next dose in they are real weak, and the hobbyist doesn't really know what they had at what concentration. People worry so much about their fish that they often shorten dosage time with Meds as well. Meds can be and will be effective but only if used properly within set guidlines in a clean tank for the same period as salt. Most people won't do this with sensative fish (I know I didn't like to) and many sensative fish won't take the stress. Salt is much much easier on sensative fish. For the time period it takes to treat ich, very few fish will even show signs of stress. Pictus, some cats etc. will show some odd behavior, but not nearly what they do with meds.
Now for the practicality of things. You are already pretty deep in this, but nothing can change that now. Raise the salt level to 1 tsp per gallon slowly. Put you Ac in the filter as soon as you reach 1 tSP per gallon. Continue adding salt until you reach 2 Teaspoons per gallon. Once two teaspoon per gallon is reached, you can relax a bit, but I would suggest doing some water changes to gt rid of the meds. Just make sure you put 2 TSP per gallon of salt in you change water before it goes into the tank. give the AC 2 days, and chuck it. then if you think you need to add AC one more time.
Since your Loach has already been through an extended battle with ich, and most likely your other fish still have it sub clinically, you need to understand that there may be more fish deaths. I hope not, you hope not, but the reality of your current situation is what it is. Do the best you can and learn from it all you can. Turn the lights off to help relax your fish, keep the water as chemical free as possible and feed very very lightly if at all. You may get through this with flying colors, and you may not.
As far as temp, I did not expound well enough in my article on this subject. Ich dies at 86*F I did state that. therefore the closer you get to 86* the better, but any rise in temp will shorten the treatment period and help your fish. My personal method is to add the salt first to the level I want and then slowly raise the temp as high as I can until the fish react. It is best to get the temp up to 86* but any extra temperature will help with treatment so if your fish react to rising temperature harshly, then stop incresing for a while and see how they act. if they settle down, increase it a bit more until you get to your target temp. if they don't settle down, leave things alone. once the salt is in the water your fish are protected from further outbreak, the temp speeds things up and gets the ich off the fish which in turn lowers their stress levels and lets their wounds start healing. If the fish seem to be bothered more by heat than they are by ich then take some extra time with the ich and hold off on the heat. With my pictus cats, ich is by far the greater irritant, and therefore the extra heat helps them out the most.
HTH
Dave
Dave