As for "not just depend on each other, but that they are unity" - I don't see the difference.
The difference is tremendous, although quite difficult to grab. If you reduce the number of space dimensions to 2 it would not be hard to imagine time-space as a brick or a bar of butter or cheese where two coordinate planes represent space and 3rd stands for time. If a physical point moves in space it draws a line inside that bar of butter. If I take a knife and cut that cheese I will get a number of 2-dimensional sections with a point in it which stand for momentarily space coordinates of the physical point in a known point in time. The difference between Newtonian absolute space and time and Minkovsky perception of the space-time model is that Newtonian concept treats time as an absolute entity completely orthogonal to space. In other words you can cut the butter only at right angle to the space dimensions and you'll always get sections of the same shape with the same coordinates of the moving point. It's not the case with the space-time concept. Time is not absolute any more. You can cut the bar at different angles and get different coordinates of the moving point at the same moments of time in different inertial coordinate system moving with different speeds relative to each other. And there is no such a thing as the absolute coordinate system. More than that, if the moving object is not just a physical point but has distinct space sizes - length, width, height you will notice that tese sizes are different from the point of view of different coordinate systems. So it shows that time is not absolute, it can be actually converted into space and vice-versa. And if time can be turned into space and vice-versa it means that time and space have the same nature, they are made of the same fabric, if you excuse this parable, and they create unity.
Anyway it looks like philosophy rather than physics. Philosophy can not predict results of physics - their subjects are different.
Well, you have a point, but let me state my opinion that any physical theory is based on some philosophical concept. Newton was a devoted Сhristian and that laid an imprint on his perception of the physical world. Absolute Time orthogonal to Absolute Space, the main coordinate system attached to them - all this concepts are in total concordance with the idea of Absolute God. Einstein on the other hand was a follower of Mach's philosophy and it shows in his theories.
Well, unlike faster-than-light travel, it doesn't blatantly violate known laws of physics
The problem is, the impossibility of faster-than-light travel is not explained by any known law of physics. It's postulated "as is" and the whole physics theory is built upon that postulate. It's overall accepted, it's proved by innumerable experiment and observations but it never has been plausibly explained.
On the other hand, today's real-world physics predicts that IF Einstein-Rosen bridges actually exist at all, anything much larger than an electron would be crushed into "singularity" while attempting to pass through the wormhole. So, science-fiction which depicts ships going back and forth through wormholes is essentially "stealing" a valid concept from modern physics and using it in Magical and unrealistic way -- they might as well forget any pretense of science and solve the problem of interstellar travel by using the Floo Spell from Harry Potter!
I agree, but please remember, that however modern and strange and complicated the relativity may seem in fact it is a classical physics theory in the sense that it isn't a quantum theory. So nowadays it is perceived as outdated and needs to be redesigned in order to be built in the modern quantum perception of the world. As for the quantum theory, it opens doors to almost boundless flight of fantasy and speculations.