Interesting! I'm not sure if all the changes increase verisimilitude, but they certainly will be less frustrating for PCs (at minimal flavor cost).

I like the idea of, say, construct specific diseases. I'd imagine they'd vary by type too. I can see flesh golems as being vulnerable many of the same diseases that harm humanoids; such diseases can infect and destroy their flesh just like a human's. Of course, if one's putting all that money into making a flesh golem, it makes sense to make them immune to tentanus and gangrene while you're at it, lest your creation lose limbs over rusty nails or paltry other injuries. A special strain of a metal-corroding disease could be cool, harming animated objects, golems, and the like. Perhaps it's attracted to any sort of metal with a magic aura, posing a threat to magical swords and such too. Anyway, perhaps just note for every disease which sorts of creatures it can affect and which it wouldn't work against. Same for poison, I suppose.

Giving everything a Constitution score is nifty too.

Actually, looking through these more, I may implement a few of these changes in my setting (if you don't mind of course). Some are pretty nifty and would potentially make the game a lot more fun.