I'm sorry to hear how much your sexuality is causing you some distress. I want to start off by saying that there is nothing wrong with you. Sexuality is a big, messy thing that is experienced in many different ways and can take some time to figure out. First, I want to answer a couple of your questions you've posted about asexuality and feeling some conflict between having certain sexual thoughts and desires for things like masturbation but not for other romantic or partnered sexual relationships. Asexuality is a huuuge spectrum that is experienced in a lot of different ways. How you have described your sexuaity can be one way that some people who identify with the label of asexuality experience it. You can have desires for a close relationship with someone where you both prioritize and care about each other, while not being romantic or sexual. At 16, being in this area of questioning is more than ok, and frankly quite normal. Like I said before, it can take some time to understand and your sexuality can also change, especially as you explore other parts of your identity, and that's also totally fine. All this said, I cannot tell you whether or not you are asexual or aromantic because that is something that only you can know for yourself. But, below are two resources that you may find helpful.
I completely understand wanting to have an answer right now and how it can be frustrating not being able to fully describe these conflicting things you're feeling. What's most important is that eventually you get to a place where you feel comfortable with your identity and where you don't feel like you are having to fake anything with anyone.
After reading through those resources, does anything feel relatable for you? Or bring up any other questions/thoughts? I know I didn't quite touch on everything you have mentioned but I first wanted to give you a couple of those resources. If you want to talk about your feelings about masturbation or your gender identity more, we can do that too.