Think AMS airport will be any better in September?

I wouldnt count on it being better.

From what I have read, here and other news sources, the bigger problem is starting a flight at AMS rather than a plane change.

Will it be better in Sept.? Hopefully by then the staffing issues will have been fixed , or at least less troublesome, and thing will operate more smoothly. Or by then the airlines will adjust the flights to build in more time for transfers.

The reports I have seen re: AMS have been getting through security when departing from AMS. Transiting AMS, staying airside, is not supposed to be bad.

I transited AMS May 28 with zero difficulty (incoming KLM Vienna flight, outgoing KLM Atlanta flight).

The problems at Amsterdam Schiphol Airport mainly (only) concern those who are departing and arriving. Transit passengers who booked their flight on 1 ticket can remain airside and don’t face the issues of going thru security etc that departing passengers face.

Transit is not near the issue. I think you would be fine with your connection.

Based on what I have read once you are in the airport it's not horrid... the problem is getting IN the airport!

We transited in AMS on June 10th. Inbound KLM from Florence. Outbound Delta to Seattle. There was a lot of running and sweating to make our connection, but not because things were amiss at AMS. We had a 1 hour 15 min layover scheduled at AMS and took off 1.5 hrs. late from Florence. Yeah, not good. But, thankfully, our departing plane was also delayed and we managed to be the last people aboard before they shut the doors. I think all told we were on the ground for about 25 minutes and made it from the B terminal to the F terminal in that time.

We're strict adherents to Rick's packing lists and don't check bags, which paid off yet again. I do think that I may take up jogging again (at the age of 63), just so I can train for what air travel has become!
Good luck!

Last September we had a layover of a bit over an hour at Amsterdam. We were flying Delta/KLM. The plane was a bit late. We made it but when we got to our connecting the plane was boarded and they were clearly waiting for us. I doubt they would have waited much beyond departure time. I would use the Delta app or have a map of the airport and know the route from one gate to the next. There is a line at passport control with people with short connections. If we had to go through with everyone else, we never would have made it.

Again, I'm thinking of booking a cheap nearby hotel for my transit day in to Europe , also in September, and transit day home from AMS, just in case.
I'm also coming from Florence going home, and that airport is always having planes leaving late in my experience from past trips.
At least I'd have somewhere to sleep in case of big delays or problems, and not have to sleep in the airport.
If I didn't need the hotel, I wouldn't be out too much money.

If anyone can reliably predict what travel will be like in September, please tell me who's going to win the third race at Santa Anita

"please tell me who's going to win the third race at Santa Anita"

That's too easy, the jockey wearing the white pants always wins, that's how insiders know who to bet on.