In future years, could the Hulman (edited) Hundred return to Indiana Fairgrounds the weekend after Labor Day. Leave the May race as it is - add another in Sept

I think it's good where it is as part of the lead up to the Indy 500. (Hoosier 100 on original post.)

Make it the Hulman Hundred that weekend.

Then run the Sumar the night after the
Tony Hulman Classic at THAT!

The schedule this past May worked well. The Tony Hulman Classic on Wednesday followed by the Hoosier Hundred on Thursday were both very successful. I hadn't seen a crowd that large at the Hoosier Hundred in ages. I did not attend a USAC event on Friday night, opting for the Josh Burton Memorial on Friday.
I never attend any events on the Saturday before the 500 due to logistics, so I can't comment on those events. On Sunday I attended the 500 and the Sunday night races at Haubstadt. I would prefer they leave the Hoosier Hundred as it is now because I couldn't attend if it were the night before the Brickyard 400.
That is my $.02 worth.

"Leave the May race as it is - add another in Sept" (like it used to be right?)

yep