The Sims 3 64 Bit Keeps Freezing

@Atheist_Monk  I have no idea whether this issue will get addressed, but I do know that EA is keeping an eye on the issues reported here.  The question will be whether the problem has a simple enough fix.  If it took reworking the graphics engine, that would probably be too much work, but perhaps there's an easier intervention.

I understand why you might not want to keep working on this, but if you felt like experimenting, you could try editing some of the values tied to the lighting setting in graphicsrules.sgr.  It may be that one particular value is the issue, and you could set it to low while leaving the others as is.  To be honest, I'm not totally sure editing graphicsrules has an effect anymore; it seems like something else in the game is overriding at least some of the settings.  At any rate, it doesn't hurt to try.

To access graphicsrules, find the Sims 3.app wherever you installed it.  (The default is the user Applications folder.)  If you see a Sims 3 Pack folder but not the base game .app, hit cmd-shift-. (period) to show hidden files and folders.  Right-click on the .app and select Show Package Contents, and from there open:

Contents > Resources > The Sims 3 [right-click, Show Package Contents] > Contents > Resources

Make a copy of graphicsrules.sgr for safekeeping, then open it and cmd-F to search for "lighting" without quotes.  You'll land here:

option LightingQuality
    setting $Low
        prop $ConfigGroup ShadowMapSize 1024
        prop $ConfigGroup RenderShadowsEnabled false
		prop $ConfigGroup InteriorLightProbeCount 3
		prop $ConfigGroup LowDetailLightmaps true
		prop $ConfigGroup ShadowColorFormatWorkaround $intelShadowColorFix
		prop $ConfigGroup HighRezTranslucency false
    setting $Medium
        prop $ConfigGroup ShadowMapSize 1024
        prop $ConfigGroup RenderShadowsEnabled true
		prop $ConfigGroup InteriorLightProbeCount 8
		prop $ConfigGroup LowDetailLightmaps false
		prop $ConfigGroup ShadowColorFormatWorkaround $intelShadowColorFix
		prop $ConfigGroup HighRezTranslucency false
    setting $High
        prop $ConfigGroup ShadowMapSize 2048
        prop $ConfigGroup RenderShadowsEnabled true
		prop $ConfigGroup InteriorLightProbeCount 20
		prop $ConfigGroup LowDetailLightmaps false
		prop $ConfigGroup ShadowColorFormatWorkaround $intelShadowColorFix
		prop $ConfigGroup HighRezTranslucency true

You can change the settings under High one at a time to see whether anything makes a difference.  Like I said though, I'm not sure it will; it's just worth trying.  I'd do it myself, but so far, I haven't had this issue.