For the message "system process not responding", it is caused by gapps (googlebackuptransport.apk more exactly). We will update them for next release. If you need a workaround, try to change googlebackuptransport.apk in /system/app/ from another recent gapps . Anyway, that message doesn't affect anything in daily use.
For OTA app, update notifications can be effectively disabled (except at boot) in next release