Some of the transformations that would be required in u/Saedius' protocol would be so low-yielding, and / or the desired product such a small component of a complicated mixture, that you'd need to spend use a lot of time and resources to generate them in reasonable quantities and purify them.

Solids generally react only very slowly with each other, unless you put some energy into the system (e.g. by grinding them together) or the interface between them melts or liquefies somehow.

In the case of a frozen block of acid in contact with a piece of acid-reactive substance, there would likely be just enough melting or water vapour condensation at the surface to allow a reaction to occur -- this might in turn generate heat, that would keep the reaction going.

This is a great answer. TBH I've always found it odd that we teach the concept of "ionic bonds" in introductory classes. IMO thinking of them as bonds can be very unintuitive and misleading, for the reasons you reference in your answer.

Yes, but it gets tricky to scale up purely chemical processes for protein synthesis (making small quantities is easy, making larger quantities gets expensive and complicated) -- and the problem gets worse, the larger the protein gets.

As already mentioned -- protein expression in bacteria is usually more efficient.