It might be time for SBS 2011. Maybe get a fresh start this time with a full reformat/reinstall instead of a bare metal restore. This will be time consuming. Maybe use a different HyperVisor. Or just get a new server entirely. The new LGA2011 socket just came out too and it's been 4 years. Then again I always try to find an excuse to upgrade

Sounds like you're having a lot of issues. It may not be worth your time troubleshooting and trying to fix each one. If possible, consider a complete reformat/reinstall.
Can you describe your current setup? You have a XenServer and a SBS 2008?