1) Yes Kordon Rid Fungus is effective against Ick
2) Kordon Ich Attack is also effective against Ick
3) To the best of my knowledge/research, the two Kordon products mentioned are both exactly the same meds/ingredients and just have different labels for marketing purposes.
4) As far as I know, Maracyn and Maracyn 2 (not effective in high pH/GH) only treat some bacterial diseases, and not parasitic (which ick is a parasite).
5) I know Purigen is different that activated carbon/charcoal, but not sure if it strips out meds or not, best to remove it just in case.
6) I know Kordon Rid Fungus/Ich Attack (not Kordon Rid Ich), is safe for plants, inverts and is very well tolerated by fish.
7) Regarding temps, I am not quite sure, as far as the med itself, it shouldn't be rendered useless at those temps. However, raising the temp will speed up the life cycle of ick, which can mean the ick will potentially die faster during treatment OR it could mean the ick will reproduce faster and worsen the condition of sick fish faster if the med isn't strong enough.
With that said, when I use Kordon Ich Attack, I don't raise temp at all. Usually safer/natural meds are not as strong as those other harsh chemicals out there, so it is a trade off, safer for the fish, but not as fast/strong acting, so don't expect the fastest cure. If I were to raise the temp, I personally wouldn't do so until after the second day or so or treating, just to give the meds sometime to take effect before speeding up the ick cycle.
This stuff works great and fast for mild to moderate cases of ick outbreak. For severe infestations, again the med not being as strong as other harsh chemicals, it can take a while longer treating with natural meds, but I still believe they are the best option. If you had a fish seriously covered in ick cysts, it would be super stressed and weak, and adding a harsh med on top of that would almost certainly kill the fish. With the safer, very well tolerated (minimal to no added stress), natural meds, they will take longer since they aren't as "strong", but being gentle on the fish will give it the best chance of pulling through.
From my personal experience with the heat and salt method for ich, my fish didn't tolerate it well at all (pretty stressed, I am pretty sure from the treatment, not the ick itself). I followed directions to a T, tried it for over 2 weeks, plus I vacuumed daily, while it treated the ick, it didn't completely cure it for me. Not to mention nearly all my plants died. I have not tried the +86*F with no salt method because my fish didn't seem to tolerate the high heat very well (I did provide extra aeration, I guess I could have pushed it and they might have survived, but I didn't like seeing them stress out). Didn't have any inverts at the time so I can't comment.
Just my experiences and opinions though, yours/others may vary.
So if it were me, I would definitely use Kordon Ich Attack, even over the salt + heat or heat-only methods, but it's your call, just keep a eye on how the livestock deal with it, if you kill the very ones you are trying to save, well then, mission not accomplished haha.
IMPORTANT! Regardless of whichever method/treatment you use, make sure to treat for at least a Extra 4 or more days after all visible signs of ick cysts (those visible white spots) have disappeared (as other life stages of ick are still present).