Technical problems with Nexus 7
You should go to McAfee settings there is an uninstall option somewhere in the settings , on pressing that McAfee will ask you if you would like to remove it from device administrators , continue with the uninstallation from there.

And , for your immediate issue , I think your device has got a serious virus/malware or may even have been hacked , which is causing remote control by someone( I don't know if I am exaggerating a bit).

So firstly try killing all the network connections , manually remove  sim card (if your device has it) and turn off the Wifi router and then observe if those issues persist.

If issues persist factory reset your device , but prior to it take a backup of all data(or I think you should not because it will carry the malware with it so do accordingly).