I would go buy a new flapper and try that, because, I agree, that chain looks very tight. The plumber who installed it, may have shortened it? Did you get the paper work, that came with the inside the tank parts? That may also give you some information. When the chain on the flapper is too tight, it closes too fast. You also do not want it too loose, because, then it takes too long to close down, and doesnt flush well. U tube has several videos on installing flappers. You might want to watch a couple before you install a new one.

I found this for you. I also looked on the installation sheet that came with mine, and it says the exact same thing.

If your water level is more than 1 inch below the top of the overflow pipe, it may be that the low water level is not enough for a good flush. Raise the water level to within 1 inch of the top of the overflow pipe using the water level adjustment screw on the fill valve or by adjusting the height of the fill valve.

"I adjusted the roller clamp..."

The roller clamp only adjusts the rate at which water flows into the toilet bowl, not the amount of water the flows into the tank.

The length of the chain doesn't control the amount of water that fills the tank which you say is too little.

1. Flush the toilet and let the the tank fill until it stops on its own.
2. Press down on "A" in the photo below. Does the tank continue to fill?
3. If so, turn "B" (which adjusts the height of the water in the tank) until the water fills the tank to the desired height.
4. Adjust the roller clamp so that water finishes filling the bowl at about the same time the tank finishes filling. You don't want to underfill the bowl but you also don't want water to continue to flow into the bowl after it's full.

I followed @wdccruise instructions. No change. Same level as you see in the photo. I don't think I can raise the height anymore if I want to be able to use the cover! I can't imagine that now changing the flush valve will do anything differently; the chain is the same length as the original since both are from American Standard. But what's left?? This is weird because it only started when I changed the fill valve. The flush feels better now though.

I wonder why American Standard didn't send me that one. They sent me this one.

Some questions can never be answered.

Are you saying turning B doesn't make a difference in water level? It should.

Ruth Ann, you dont have to have them send you one, you can buy them in almost any hardware store.

@klem1, that's correct. Might be faulty.

@cat_ky, yes, I know. But it's under warranty. If the replacement doesn't work, I may look to buy that other one.

If the screw doesn't cause less/more water in tank the valve is without doubt defective but those Fluidmaster type valves are inexpensive and stocked everywhere plumbing is sold.