I honestly think the comparison to his son is another way for him to be manipulative. Telling you he loves you so openly is weird and unprofessional in any context. I think he uses the fatherly angle to inspire trust and for him to come off as sweet instead of creepy. In my opinion none of his behavior is accidental- he knows exactly what he's doing. I hope you don't mind me being too blunt, but I don't see anything resembling a therapeutic relationship from your post; I really think he's grooming you.