Hello Felix,
I'm just reading your essay. It's exceptionally clear and well-written in addition to being well-reasoned. I believe I agree with your findings essentially and would even want to drive the thinking further. I'll try to write down some of the thoughts that spontaneously occurred as I read the essay.
When you say
"The phenomenon of quantum field theory (QFT) has no analogs in the history of science. There is no branch of science where so impressive agreements between theory and experiment have been achieved."
It's hard to say how much of that very precise experimental agreement can be credited to QFT. Though the Dirac equation is far from perfect, it's outstanding numerical success for certain calculations seems to be the star performer. Would it be fair to say that it was acquired by QFT rather than having been derived from QFT procedures? The related Dirac Lagrangian is an important part of QFT but we should probably remember that all Lagrangians, specifying path independence, are no longer applicable in a topology that is not simply connected and so have limitations. The quote by Dirac which follows really sets the tone of your later arguments nicely.
This statement you make is critical I believe:
"Then a very important observation is that, from the point of view of the measurability principle, the space has a physical meaning only as a space of events for real particles while if particles are absent, the notion of empty space has no physical meaning. Indeed, there is no way to measure coordinates of a space which exists only in our imagination."
That very much reflects a point I make in my essay that the source-less Maxwell equations (for vacuum) that are used as the foundation on which the Lorentz transformation is built do not apply rigorously to any body with which you are making a measurement on. To perform a measurement you must move a charge and then it becomes necessary to employ the Maxwell equations with sources.
Lorentz, in his book on electrons, specifically states that the Lorentz transformation is proven (valid) only in a vacuum. Voigt states also that his transformation is valid only when the the divergence of all fields is zero. The E and D fields are, in principle, zero only when there are no sources. This presents a real conundrum which is difficult to impossible to resolve within the space-time paradigm.
I'd gladly discuss more details as time permits.
Steve