Marcel, not so easy to dismiss...
"Let me put it this way. The groups 1 and 2 that try to answer the question 'what is space' are wrong in the question itself"
What specifically is wrong with the question?
"Space is a construct of our mind and already carries dimensions"
Are you saying that without minds space cannot exist? If there were no living things or if there were only bacteria in the universe, assuming bacteria don't have minds, will there be space? If not, was there no space in pre-historic times? What do you mean by carrying dimension or do you mean having the attribute of dimension? If so, can something that has attributes which physical objects obey (like Newton's first law of motion) be said not to exist? Can physical objects obey what does not exist? Or do you mean, space is just a principle?
"What substance makes the vacuum"
What is the meaning of substance? Does substance occupy space? Which comes first then, substance or space? Can there be substance without space or the opposite space without substance? Is something (vacuum) made from a substance, not a substance also? Is there a smallest substance?
"Metaphysics..."
My dictionary says: branch of philosophy concerned with being and knowing. Is physics not also about being and knowing?
Akinbo