I live in the snow belt, so my spare wheels go for a good set of snow tires. I am currently on the Sumitomo HTR AS P02 tires, a decent, cheap all-season. But, even the best all-season tires (Contis, at least from the standpoint of wet/snow safety) are not up to the same level as an average top-tier summer tire. Also, the summer temperatures and track temperatures in Cleveland aren't the same as in Florida, so that may (or may not) help with the heat issue.
That's an interesting idea to take the money saved with the Indys and spend it on a sway bar. I find the H&R bar is much more money than the Eibach, which is only slightly slimmer (but hollow?) I know the H&R is popular, but I've never seen a direct comparison. The Moog end links are "because you have it all apart anyway, and they will last" I'm assuming, not because they would help with the handling directly.
Going with cheap everyday tires to maximize my autocross tires... I'm not sure that would work *for me*. My car is a daily driver that I autocross, not an autocross car that I drive daily, if you get my meaning. That is... the autocross part isn't as important to me, it's just fun. It may be different for you, of course, that's fine. But, I'd rather have the steering precision and handling of the Michelins every day, and give up bit of time on the autocross (vs. the track-day-focused RE71R's).
The Moog endlinks are because a large swaybar and 1g cornering = broken plastic stock endlink. MS4S have more grip than Indy's, Indy's have better feel. I've got the Indy's on my son's 2018 GTI.