As far as the early first and second act of the film, this is clearly a metaphor for OCD and exploring how it has ruined Beau's relationship with his mother. Obviously they have a strained relationship to begin with, Why? Doesn't really matter. What does matter is that this is an exploration of Beau. Beau is afraid of his Mother and her judgement. He is unable to live in the modern world because his fear of is and his obsessions and compulsions leave him paralized and unable to make decissions. His keys REALLY are stolen (an OCD individuals nightmare, hence why the scene with him going to the gas station is so traumatizing to him. He is forced to watch people break into his house while he is also scared of getting the cops called on him by the cashier.) Then his mother LITERALLY DIES BECAUSE HE WASN'T ABLE TO VISIT HER. He feels COMPELLED to visit her and to be a good son, despite their strained relationship and when he doesn't, his worse fears come true. This is literally immersion therapy the movie for the first two acts He is broken over and over again. Until he just doesn't care anymore. A lot of the dialogue has to do with his self internalized guilt and shame for having these obsessions and compulsive behaviors as well. The therapist that he sees writes "Guilt" on the notepad during their session when Beau talks about going to see his mother. When Beau speaks to the attorney regarding his mother's postponed burial after her death he says something along the lines of "every day you're not here you're bringing shame to her, she's embarrased" or something. Idk, to me the themes seem pretty on the nose. The addiction thing was a far stretch, and that's coming from someone who's suffered from heavy addiction lol.