Tailoring tweeter output

I used to listen with grills off. Now I prefer the sound with the grills on. With the grills on I hear the music. The speaker becomes more seamless as if the speaker grill is the first stage of room treatment.

Sure, you might hear more detail in some area of the sound without the grills, but it be at a price.

After looking at pictures of your system I see the problem.
You are set up on the short wall. Your speakers are too close to the side walls.
Can you arrange your room so your system is on the long wall. The sound will be much more pleasing.
The room is a complex part of the system.

How far apart are the speakers?

It doesn't make sense that you can move your system from the short wall to the long wall with the same results. The long wall should give you more options for speaker placement and the ability to increase off axis listening angles.
The fact that the bass was a problem on the long wall was most likely midbass which is easily cured with Tube Trap products along with Tube Trap products for the wall behind the listening position.
I know there are other room treatment products on the market, but it is my opinion ASC makes the best room treatment.
I see you have analized your room to death, but there is nothing like trial and error.
Sometimes we have to take two steps back because we went too far. Room treatment and cables alone are extremely powerful.
This is all a delicate balance and sometimes when we think we need less of one thing we actually need more of something else.