Okay...I completely respect your opinions but let me explain
Why did it end that why? Because that was the story I wanted to share. I didn't want to go into the post-break-up and there is no sequel. Why does everything need a follow up? Why do all stories need a resolution? That isn't how life works and especially how break-ups work. Frank might find love (probably will since he is young) but maybe he won't. This isn't Frank's life story but rather a snippet of a moment of his life. I wanted the film to feel like that. It is an arthouse film, which doesn't follow the traditional storylines/plot devises of mainstream books, TV, and films.
Also with Frank's father. It is meant to add to the atmosphere and fear Frank has. Frank isn't open with his family about his deep and meaningful relationship. He is on pins and needles trying to hide it. I didn't want this to be that generic "your religious family finds out and all hell breaks loose coming out film" THIS ISN'T A COMING OUT STORY. It is a story about first love and how sometimes fleeting it can be. The scene with Frank's father builds the atmosphere of tension and a foreboding sense this relationship with Mark is not going to work out. We know Frank has curfews, is in a religious household, and is dating a guy much older than him.
Also with the "left-field" lady coming in and tell Mark about his past. Yes, that is out of left field and meant to be. This isn't Mark's story. It is Frank's. I wanted the audience to feel lost just like Frank did. (That's also why I did the POV shots in the film). In the film, Frank doesn't understand why Mark is over the relationship and he will never realize what happened. My film Academy also touched on this. Why does everything in life need a happy ending or just even an ending. Things in life sometimes just have an open ending. That's kind of the lesson I wanted to show here. ( Feel like I am repeating myself lol so I am gonna stop).
Ultimately, I wanted to make the audience walk in his shoes, be confused when he was confused, and joyful when he was joyful. I completely understand your problems with the film but I made them there because that is the story I wanted to share.