Questions on writing a character with a stutter

Questions on writing a character with a stutter Hello Reddit! I am working on a story that includes a character with a stutter. Since I don't have one myself, I wanted to reach out to people who do, to ask for some feedback on the character I am creating and ask for some advice. I apologize in advance for the fact that this got so long! I'm still early into my research about stuttering, and I wanted to make sure I understood what felt like some critical info, especially since most google results were about children and parenting. The character in question had a traumatic brain injury about fifteen years ago that resulted in some temporary language and learning difficulties, and a permanent stutter. He thought the stutter would be temporary like the other symptoms, and when he realized it wasn't, he had some difficulty adjusting to his new speech patterns. By now he's aware of what sounds most frequently to cause problems for him (P, G, D, and B) and consciously avoids them in conversations. Since his injury, he's developed a rude personality so that people won't try to talk to him unless it's necessary. He doesn't engage in small talk unless it's with someone he's familiar with, as he gets frustrated by strangers trying to fill in words for him or talking over him. He's generally seen as aloof and sort of an asshole by his acquaintances. With the people he trusts not to judge him, he's talkative, generous, caring, and charming. The stutter itself doesn't bother him, others' reactions to it do. I found a study that stated that people stuttered more frequently when reading long sentences as opposed to short sentences. It had a small sample size, so I'm not sure if it would be realistic for him to prefer to speak in short sentences because they're easier for him to say. My main question is: how often would his stutter likely occur? I imagine this would vary wildly by individual, but I'm hoping a ballpark number might be able to be provided. One source from [The Stuttering Foundation](https://www.stutteringhelp.org/differential-diagnosis) suggested once in every ten sentences, but the article was focused around children who stuttered as they were learning to talk and I'm not sure if it would also apply to the character I'm writing. I've also read that a stutter is worsened by stress, excitement, pressure, and fatigue. Are there other things that make a stutter worse? How much worse do you think this might make it? Another main question: there seems to be several 'types' of stutter. They were referred to as repetitions, prolongations, and blocks on the sites I was reading. Do people typically only have one 'type' of stutter, or is it more common for them to have more than one? I was planning on writing him with solely repetitions, repeating single syllables. For example, 'bet-better', 'gui-guitar', or 'bor-boring'. Does that seem accurate? And if a word had two 'problem sounds' in it, for example 'goldfish' has both G and D, would he stutter both sounds? Related, I read that a stutter is most likely to happen at the beginning of a sentence but may happen at any point, that it may disappear for a few weeks or months at a time seemingly at random, and that a stutterer's pattern of 'problem sounds' may change. Is this accurate? I read some past threads on this subreddit where other authors asked for writing advice. The responses said that the character should not be written as comic relief or a nerd. They also said the stutter should not disappear because a person becomes confident or undergoes character growth, and it shouldn't be their only defining characteristic. Are there other things that I should avoid? Or on the flip side, is there any characterization that you would prefer to see? I feel like I should apologize a second time for how long this got! I appreciate anyone who reads through the whole thing. Your answers will truly be invaluable to me. And if it seems that I should rewrite this character to not have a stutter because I don't know enough to do it properly, please let me know.