My buddy swore by spit for years, then found out he just needed new glass lol.

That inspector is overselling it. Older codes used to allow screws every 16 on ceilings all the time and plenty of those houses are still standing 40 years later without cracked seams. If your framing is straight, your board is tight, and you didn't skimp on mud, the screws aren't the weak link, the joint compound is. Tearing open finished rooms to add screws you probably don't need is a good way to CAUSE the cracking you're trying to prevent.

8 months though? That thing must have been sitting there judging you every single day when you walked past it. I can't believe you made it that long without just tossing it on marketplace, most guys would've cracked after a month. The part that gets me is the screed probably costs more than what you made on the pours you did instead. Maybe hold onto it till spring and see if a bigger job pops up, but if not, sell it and put that $180 toward something you'll actually grab.