ArnO- Although you can CA the foam as a fix, it will consequently cause a hard spot where the CA is and can cause more tearing or inconsistent wear. I prefer to use contact cement to fix tires as it stays flexible and wears with the tire.

Second thing, ditch the black tape for holding in the batteries and get some fiber reinforced strapping tape. Black tape will stretch out and let the batts move around or come loose.

For the servo issue, if the links are the same length and its still not centered, then the servo itself isn't centered on the chassis. If you can wiggle it into the right position I would adjust the link length so the servo saver is straight. That will keep the ackerman equal in both directions. I would also recommend moving the servo up to the top holes on the mount. The severe downward angle of the steering links will cause bump toe-out which will make the car hard to drive.