I need a SOCKS/Proxy server that is capable of using SSL certs.
Additionally, I want it to ONLY be able to connect to 2 domains.
User authentication is not mandatory.
AS far as I know, SQUID is not a SOCKS server.
WinGate has a SOCKS server, which supports client connections using TLS/SSL including client certs (which is non-standard) which authenticates to the proxy based on the UPN in the certificate (when using the Active Directory connector in WinGate). You can also with policy lock the destination down to wherever you like.
Disclaimer: I work for Qbik who are the authors of WinGate