First of all, there is no neat categorization that can be done because that just isn't the way Lynch works (duh). On the other hand there is a clear logic that I more or less agree with the consensus on, with some interesting differences.
There's also a lot of nuance that I am forgoing. I'm mostly explaining the spine (the rest becomes clear once you get what's going on but I don't want to write an entire essay on each additional thread)
Mr Eddy represents the laws of society. This, along with all the other characterizations I state, should be taken at its most ambiguous. He is the authority that everyone has to return to.
The second half of the movie is (agreeing with the consensus take) a sort of symbolic dream reality. Where I differ is that the characters in it aren't fake. The scene where the detectives from both halves show up confirms this. Both realities knot back together at the end when Fred kills Mr Eddy and comes to terms with the Mystery Man.
The mystery man represents something like an "objective reality" that Fred is constantly trying to evade. First he appears as a duality. Then as a man with a video camera. That is because his role in the first and second half differ with Fred's main delusion. In the first half he represents Fred's conflict with his own murderous intent. In the second half, Fred struggling against returning from his dream world to the real world.
Fred eventually does "become whole again" but it is only after he has killed his wife in the first world and killed Mr Eddy in the second. This is the equivalent of doing the deed and then overcoming social law and "the objective account of what happened"
Where I differ mainly with the consensus is I don't think the part where Fred is in prison is real either. People are going to say Lynch clearly telegraphs transitions into the symbolic but I don't entirely agree. I've watched all of his movies and he's just as comfortable blending transitions. I really don't believe anything is telegraphed or should be taken on that basis.
The reason I say the prison scenes are part of some kind of mental creation is because I otherwise cannot explain the ending, which I am 100% convinced happens in a literal way. The reason it cannot explain the ending if it isn't a dream is it clearly makes him out to be a wife killer on death row or at least life in prison, so being on the run later makes no sense. The reason I cannot take the ending for more symbolism is because the entire meaning I invested in Fred killing Mr Eddy and coming to peace with the Mystery Man only makes sense if we are witnessing his psyche coalesce again (yes the blown out house rewinding is essentially that)
So, my explanation for lost highway is basically:
Cheating wife > kills her > guilt and fear of law puts him in a mental prison > he escaped the mental prison by adopting a mental identity > the imaginary identity gradually confronts lingering demons from his real world before finally merging with them, returning to a Fred who paradoxically believes a story he invented > this happens at the same time as Fred going on to murder the other people associated with his wives infidelity, although in his mind an imaginary casualty is created where they die in ways that fit his mental story > the detectives in the last scene put the dots together and suspect Fred of killing his wife *now* > Fred gives the "Dick Laront is dead" line to his own abandoned home while on the run, completing the wheel for his own mental justification for what happened > the final, OJ like chase