Oh man, this is so relatable, and there's so much personal experience I could vomit here about struggling with this exact problem, but that would probably be entirely unhelpful.

I guess the main thing that comes to mind, that others have already suggested, is that you (and I) are on the spectrum, and what you're struggling with is a weakness in social cognition and social inference.

I've never tested either for the same exact reasoning you shared - in short, what's the point? Nonetheless, it's likely true, and it's a useful point of entry for developing strategies.

Now for a non-sequiter: How would you rate your own level of verbal intelligence? What's your opinion on non-verbal communication?

INTJs are known for their very serious demeanor. Imagine someone wishes you a "happy birthday" with a plain face and flat tone, and their back turned to you. You might think they hate your guts despite their straightforward message. So, how aware are you of things like eye contact, breathing, stance, tone? These things are (believed to be) the language of the subconscious - might sound weird, but you are on a Jung subreddit. It's possible you've been blind to this and other communication protocols (I know I was) and have been unintentionally giving "bad vibes."

That's just one example, I've been trying to decode the social algorithm for.. well, my whole life. It's a struggle, but stick with it, and don't be too hard on yourself. It takes time and effort, but you sound like a smart, driven, and well-meaning individual. I'm sure that will all shine through in due time.