I just purchased an 8 inch round, 3 inches deep. My cake sunk in the middle and looked all lumpy (hard to describe, almost like worms or brains in the center). It was just a DH white cake mix, no doctoring, pan greased with Baker's Joy. I did use a flower nail in it.

It appears that you have several cake issues going on... both of which can be explained by overmixing.

Handy trouble shooting charts:

http://tinyurl.com/2p5bdu

http://tinyurl.com/6c745g

http://tinyurl.com/32goqe

HTH