There isn't a way for a customer to nuke the database. What I'd suggest is backing up the LEM configuration on Dec 31, re-deploying the VM and then importing the LEM configuration. You'll start with a shiny, empty LEM with all your rules and configurations.
You'll want to be familiar with the backupconfig command from this KB: SolarWinds Knowledge Base :: How to Configure Backups on LEM Appliance for versions 5.6 and later
And the import process from this KB: SolarWinds Knowledge Base :: How to import settings from a SIM or LEM appliance backup to another appliance
You'll also need to contact Customer Service at Solarwinds to get your license reset so it can be applied to the new LEM.