1. The virus scan starting on reboot of your system is not normal behavior.
You can contact support about this. They will probably collect your logs for it.
2. The ability to disable scheduled scans is broken and is a known bug.
3. This is as designed. If you DISABLE product updates its disabled through out the software.
If we allow manual updates we have a bunch of users complaining that its not a true disabled function. With either way some one is not going to like its behavior and we decided to implement its functionality in this manner and will be staying like this.