Hey, steady on a bit there...
I don't know anything about the guy you met in high school, so I can't really pass judgement on him, or you, or whatever went on between the two of you. He may well have hurt you or treated you badly, and if he did, then it's completely fine for you to be angry and resentful of him. No-one should mistreat others, and it's understandable for people to be angry about being mistreated.
But even so, I think you might be projecting him onto Periwinkle a bit here.
I don't really think Periwinkle 'is being praised as a tragic character'. The story is told from his point of view, so I suppose it's easy to get that impression - sometimes Peri makes excuses for his behaviour and his feelings, and that could be misinterpreted as the story saying that he's right, and not just making excuses.
I think the story shows that Peri's misery is caused by his own misunderstanding, and his own reluctance to examine his feelings. The scene where he has that long conversation with Astragalus near the end, and the scene with the unnamed angry witch, both seem to show that.
(Plus, the game shows that Peri's misery is just something that he needs to understand and find ways to make better - it's something that is CAUSED by him, but not something that he needs to be BLAMED for or seen at FAULT for, like he's done something wrong, because being miserable isn't really a moral failing!)
I also don't think it's really fair to say that Peri is 'toxic' or a 'creep'. Peri seems very considerate of other people's feelings. For example, he makes sure of Pastille's pronouns when they go on their first date, and when he turns down Cassia he sees to do it very gently and tactfully. Also, when he goes to see Pastille at work for the first time, and Pastille gets upset about it, Peri seems genuiely upset and apologetic about the mistake he made, and he makes sure to be more considerate of Pastille's boundaries in the future.
I suppose you might not like how Periwinkle teases people and makes suggestive comments - I wouldn't really like it if someone spoke to me like that - but I get the impression that Peri only acts like that with people who he already knows wouldn't mind it. He's forthright and outspoken and cheeky, but I don't think he goes out of his way to upset people or make them feel uncomfortable. He may do that sometimes, but only by accident.
I'm sorry if this game and its characters brought up bad memories for you, and I'm sorry if I did that as well, or stepped over any lines with this comment.
I just thought that your comment was a bit unfair and unfounded, that's all.