whysoogrumpy I've split your post into its own thread because the other thread was getting a little unwieldy for me. It's typically easier to troubleshoot with one person at a time, with some exceptions.
Anyway, do you have Steam family sharing or similar enabled? If so, please disable it.
Did you try moving the Sims 4 folder out of Documents > Electronic Arts? If not, please do so now.
Aside from that, what antivirus do you use? Is OneDrive running on this computer? Even if you never use it, OneDrive could be interfering with the game.
I ask all this because your dxdiag doesn't list any Sims 4 errors, which typically means the game is being blocked from starting rather than crashing.