hi,
the amount of salt and rise in temperature should not kill the plants.
copper in any way has to be avoided, when you have shrimps in the tank, they die. catfish have problems with salt in the water and a few other fish as well.
the best medication is malachite-green (oxalate), although there are sensitive fish, e.g. neons, who might not tolerate malachite-green.
the idea of raising the temperature is not to kill off the bugs (that's not possible at these temperatures), but to speed up their life cycle, and make treatment act faster. it can only kill one stadium of the bug.
with higher temperature it has to be made sure, that there is enough oxygen in the water, as less oxygen dissolves the higher the temperature.
the ichtyo parasites are normal to be present in a fish tank. stress, bad water quality etc. helps it to explode. therefore the best preventative measure is to look after your tank, keep the water fresh, not too many fish, various diet, not too much food, no social stress,...
if you catch ich right at the first symptoms, it may also prove an efficient treatment to change50-60% water every day for a few days. it stimulates the immune system and reduces the concentration of the bugs (although most of them will be found in the ground, together with useful micro-organisms).
lg
niki