i dont think 82 degrees will cause any harm but raising the temp will only speed up the life cycle of the ich not help kill it off even if the garlic and the shrimp get it under control,you still have ich and it will be back.
shrimp only pick off the paracites close to the surface and probably dont even get half of each one, garlic boosts the imune system so the fish are healthy enough to cope with the problem.
if you want to be rid of ich you have no other choice than to treat it,not the simtoms of it,so if you like the fish you have and dont want a fish grave yard like the one i have in my back yard dont wait untill its too late.since loosing a 130g full of fish i have a 67g qt
tank all new fish live in,ive got ich since then and copper worked like a charm for me and recomend it to anyone with a tank they can devote just to treating fish. hypo is another meathod wich would work but my experiance didnt go well i had a lot of bacterial infections and the non stop waterchanges almost killed me lowering the salt then raising it back up uses a lot of salt up in a hurry.
so sorry about the ich but i think you need to reconsider your plan.