The best we can do is check the game's RAM usage using Task Manager once it starts up and the game clock starts moving forward smoothly, and again frequently throughout play to ensure it's staying leveled off and far enough below the danger zone. Very large, complicated, or over-populated worlds or households can lead the game to call for more RAM than it can actually use. So can extremely long game sessions without doing a Save (As), quitting to the Desktop or Origin, and reloading, as can overly long CAS or Edit Town sessions with too many town changes being made all at once.
NRaas mods that can help game performance: Overwatch, ErrorTrap, Register, Traffic, to an extent GoHere, Traveler (if world travel is ever involved), and MasterController to run a Reset Everything every few sim weeks.
http://nraas.wikispaces.com/Tips%20For%20Better%20Game%20Performance
On the HDMI connection and the 30 Hz, it's possible that I wasn't reading that part of the dxdiag correctly. @phoebebebe13 -- what do you see and do we need to call in chesterbigbird?