1. Dozens of localities have controlled the virus via lockdowns, social distancing and masking, they all show similar curves to NY but with lower peaks. NY therefore offers no evidence that herd immunity has been reached.

2. Your Spanish study shows 90% of those with a positive PCR test also had antibodies. The low symptomatic positive rate could be easily explained by other seasonal illnesses with identical symptoms.

3. There is no evidence beyond supposition that I can see for the Wuhan clinical workers having the virus. An alternative explanation is that protective equipment and protocols were effective.

4. The idea of 80% of the population being T-cell immune seems inconsistent with the outcomes on the Diamond Princess.

I think you are cherry-picking data to support a far-fetched theory. The outcomes in confined places where the virus infects everyone, like the Diamond Princess or nursing homes, seem especially hard to square with the idea of widespread t-cell immunity.

Edit: I was misremembering the Diamond Princess, not everyone on the cruise ship got the virus. However, Marion Correctional Institute in Ohio had 80% test positive for covid; the Life Care Center in Kirkland, Washington had 2/3 test positive. These don't seem consistent with widespread T-cell immunity.