Is Johan real?

There are a couple of reasons for me to wonder whether Johan is real:

- the old lady tells Alma about the sketchbook and diary in the bag under the bed. Since the lady is Alma's illusion, she can only tell things Alma knows. Since Alma starts vigourously reading the diary after the meeting with the lady, she did not know in reality, so how could the old lady have told her in an illusion? If both the lady and Johan were Alma's illusions, Alma could have learned through the lady of Johan's diary all as part of her own illusion.
- Johan is killed by the characters. If Johan were real and the characters are not, it's rather unclear how Johan did die. If they all lived inside Alma's head only, though, it would be perfectly resolvable.
- At the start of the movie, when Alma talks to the narrator, she speaks of Johan's disappearance, not of his murder. Why would she do that when he was murdered?
- Why do we never see Johan's paintings and drawings, even though they are referenced quite often?
- Johan and Alma have the exact same representation of all the characters. If they were both having illusions, the characters would look different when seen through each of their eyes/imaginations. I can see practical reasons why this would be the case, such as the not wanting to use an extra set of actors or altering make-up, but I did find it odd.

I also wonder about the Veronica Vogler character, who is referenced as part of Johan's past and therefore seems more real than the rest. Could it be that she represents a lesbian side of Alma? That would explain the scandal of the discovery better than the sort of run of the mill affair Johan was describing to have had with her. And, yes, I do realize I'm going out on a limb with this last bit.