You're not dumb at all. If you're not familiar with the goings on in BDSM there is really no way you can recognize something you've never seen or experienced before. I'm sure you did recognize that there was something off about the kid though. You just didn't know exactly what it was. Now you do. This is how we learn and why it is important to experience or at least see new things. Even if they are disturbing, that information can be added to your knowledge. Maybe you will never need it again or maybe it will come in handy later. Either way, you have it now. It is always better to have something and not need it than needing something and not have it.
LOL When I was a kid I used to read the dictionary from cover to cover during school breaks. I did it for exactly the same reason you said. It feels frustrating to not know. Now that I am much older, I tutor young people in English. I love to help and I love to teach. Seeing a student use something I taught them, and use it confidently, makes me feel very happy. If you are ever confused about words in the future, feel free to ask me. I definitely won't think you're dumb and it will make me happy to help you.
Those are all apps available on Google Play and they are all free. Human Japanese has a paid app that is more in depth, but their free app is good to get you started. I have the paid app. It was $20 USD, but it has been worth every penny! The creator of the app is actually a college Japanese Language professor and the lessons in the app feel just like a college course. They cover everything from the history of the language to the customs and culture of Japan as well as giving a detailed understanding of the language itself. You don't just learn a few phrases with Human Japanese, you learn how the language works so you can build your own sentences and phrases with your own thoughts, rather than relying on a phrase that you memorized. The way it teaches is easy to understand too. I love this app and I can't say enough good things about it. So, if you try it and want to use the paid app, contact me here through mail and I will help you get the paid version.
Just how many readers realized that the kid was an extreme masochist who would antagonize his father into beating him. His father likely beat him long before he became a masochist though and the father is also the very reason the kid became a masochist. If the only attention he received from his father was when he was being beaten, he would begin to find pleasure in the attention and eventually pleasure in the pain. The kid miscalculated when he antagonized the father too far and was stabbed. As for the vampire, he recognizes the masochistic tendencies in the kid, which is why the kid tries repeatedly to kill him. The kid knows it is impossible to kill the vampire, but he still antagonizes the vampire's wrath in order to gain the vampire's attention and the punishment he desires so much. The kid was programmed to be this way by the actions of his father from a young age. I doubt the kid really feels angry at the loss of his father, since the vampire took over the punishment and seemed to do a much better job at it. But it does make for a good excuse to antagonize the vampire.
In BDSM the kid would be considered a "brat" or a defiant masochist. This is someone who will incite and antagonize their sadist in order to receive punishment. The punishment is what the defiant masochist desires greatly. The more they fight back and antagonize, the harsher the punishment and this is precisely what the defiant masochist wants.