Rotate the tires front to rear. if the shaking goes away it confirms the front tiores as the cause which are now on the rear. Wheel balance, bent wheel, tread separation etc.

Responding in what way. Are you saying shifting smoothness doesn't change in comfort or sport mode.

Yes, I've had the problem and read here it's very common. The only way I can get it to go on is to press it before I ever take it out of park the first time after starting it. That's pretty much how I get it to turn off too. I can't see any difference driving it in that mode and gas milage is still the same so I just leave it off.

Where did you hear the growling sound (underhood or under the vehicle)? And when does it occur (driving or accelerating)?

Did you check the vehicle with a scan tool already to determine what trouble codes are present in the computer? Did you check already the condition of your transmission oil? Have it scanned and check the level and condition of your transmission oil, it may be too low or contaminated. Post the codes here so the community can translate it for you and give recommendations.

Could be but no way of knowing until you remove it now since the clutch is gone, but driving with a bad clutch for a while will ruin the transmission.