I've read this twice, pondered for a while on a few of your more vague turns of phrase. Most of my specific constructive thoughts and criticisms have already been covered by other users. I found Kaya3'sKaya3's answer the most comprehensive in terms of breaking down the pitfalls in your data analysis, but there is really something for you to glean from almost all of these answers. For my part I'm going to focus on what seems to be the root drive of your policy:
You're experiencing user attrition, and particularly seeing erosion of "eager answerers". While this is understandably eye-opening from your perspective, I think you're very obviously drawing the wrong conclusions. I won't belabor the details, but suffice to say there is reasonable doubt as to whether the statistical group you're focused on is actually correlated with high-quality answers, or whether the "lost" posts were actually a benefit to the community.
Worse yet, your blundering and unnecessarily imperious attempt at "solving the problem" is actually inflaming the true cause of user attrition: waning community trust in the leadership of SE inc. If you want to reverse the tides, that's the area you need to focus on. The solution to all your woes is as simple as it is hard:
Humility.
You need to admit you were wrong. Acknowledge that the strike was justified by your error, and roll back your decision. Then reapproach this the right way, with transparency and community involvement from the outset.
Otherwise the dedicated and skilled users that make this site are just going to keep hemorrhaging away. Which is just a shame, honestly.