My suggestion? Installing the -25 kernel? I thought alx was working; or was that the compiled version? Did the install go without error or warning? Any clues in dmesg?
Code:
dmesg | grep -i -e warn -e error
Do you think reinstalling from scratch would be worth a try?
Why??

Network Manager is not designed to manage two competing ethernet connections. I'd detach the ethernet from the Realtek, attach one to the Atheros and reboot.