I find the description quite intense. On some topics:
Site inspections during the construction phase I find at least unusual. We had a major selection appointment with the general contractor (GU), where everything was discussed in detail. Afterwards, you receive an approval for execution (huge plans for the craftsmen) which you also have to sign. Whatever is written there is how it will be done. Changes after approval are no longer so easy to make. For us, one or two things were done differently on the short route, in agreement with us on site, but that was about it. Exceptions to this: With the electrical and sanitary trades, there were separate site visits where all details were discussed. We also had to sign the agreements. Prior to that, there were appointment agreements that were kept. I assume our need for inquiries was not so enormous because we had discussed and documented most things in advance.
Regarding inquiries: We did not always receive an immediate answer. Our site manager was overwhelmed as well. If nothing came through, I asked again a day later, and most of the time an answer came. We had a WhatsApp group with him; maybe that could be a solution for you? This way he can respond asynchronously. For most questions, that was completely sufficient for us. At the handover, we saw how often his phone rang, I almost felt sorry for him. Our GU people were always easily reachable by e-mail / WhatsApp and usually responded very quickly. Phone was sometimes difficult here as well. But nothing I would complain about—especially in the context of your descriptions.
Subcontractor list / schedule: I believe one is not entitled to it (as aptly said), but we received a photographed copy. I printed the photo on A4, it looked awful but was usable. I can imagine why some general contractors don’t release that. In recent weeks, things have been shifted here and there. If the client is involved, you have to pass on every little change. He neither needs to know that, nor do you as site management have time or desire for the communication overhead.
Completion of your building: I would insist more strongly that you get an answer there. We accepted Corona (2020) as an excuse, but by now you should not be able to talk away every contractual obligation because of Corona. After all, he also signed the contract with you during Corona (ours was signed before). What does your contract say about deadlines / when they must be finished? Regarding consequences and what you can do, you might need legal advice.