So from what I can tell, there's really not much solid information available out there for this, and I am pretty confused. I'd love if anyone could give me a solid suggestion as to what I can do to mitigate this vulnerability, because otherwise I'll have to sell off this server. Thanks!
Did you search for this CVE? Because VMware has a pretty extensive article about this: https://kb.vmware.com/s/article/55806.
Mitigation of the Sequential-Context attack vector is achieved by vSphere updates and patches. This mitigation is enabled by default and does not impose a significant performance impact.
Mitigation of the Concurrent-context attack vector requires the enablement of a new feature known as the ESXi Side-Channel-Aware Scheduler. The initial version of this feature will only schedule the hypervisor and VMs on one logical processor of an Intel Hyperthreading-enabled core. This feature may impose a non-trivial performance impact and is not enabled by default.
The mitigation process for CVE-2018-3646 is divided into three phases:
Enabling the ESXi Side-Channel-Aware Scheduler Version 2 (SCAv2) using the vSphere Web Client or vSphere Client (only for ESXi 6.7u2 (13006603) and later)