Carrier/rack problems of the 2011 Nissan Altima

The dashboard is melting and cracking.

I replaced all four original tires on car in 1/2015. Vehicle had 43k miles on; tires had always been rotated and properly inflated to 32 psi. During the next months, I noticed increasing noise as the car accelerated and decelerated. I tried to determine the source of the rythmic thumping noise but was unable. I had tires inspected and no problems could be found with approximately 9,000 miles on the tires. I noticed increasing rhythmic noise but could not locate which tire was the source. We had a flat tire from a roofing nail in the rr which required the tire to be replaced. Replaced tire with another goodyear assurance. With this new tire on the rr, I was able to locate the road rumble to the right front, so I had that tire replaced with another goodyear assurance. Noise seemed to go away. As my wife is the principle driver of this car, I thought the problem had been solved with the two new tires (as one had been failing). On a 500 mile trip, I noticed that the road noise (low rumble directly associated with tire speed, especially at low speeds). I now realize that the road noise must be coming from one/or both of the original tires that were placed on the car in 2017. On close inspection of these two tires, I have noticed multiple areas of a fine splitting approximately 1 inch down the side of the side wall on both of these tires which may be indicative of tread separation. I am to the point where I feel uncomfortable taking this car on the highway. I have asked three different dealers about this and I get many assorted answers, but the bottom line is that these tires make a rumbling noise directly related to tire speed and show signs of sidewall cracking. I don't want to get to the point of an endangering blowout and am considering replacing all 4 tires in the near future. This car is driven mostly on local city street and very infrequently on highways.