If I smash the 10NES chip's reset pin, do I violate the DMCA that prevents circumvention or does my method fall under fair use like a company back in '90s experimented with the 10NES chip by pouring acid over it?
as answered before, no
and no, fair use is a copyright concept not applied to hardware.
How about reselling pin-smashed NES consoles? Or how about selling an NES console without one?
I think you're being way too paranoid, it's fine.
I think a M1 Abrahams tank will arrive at your doorstep.
Think of laws for our idiotic, money-hungry culture as this: purposefully or inadvertantly affect other companies' profits and they will get upset.
Do whatever you want but if you try to sell something and undermine another company then be prepared to buy lawyers.