It’s actually a syllabic L, which is often spelled out as a schwa in pronunciation dictionaries.
If you speak German, an equivalent would be the -en on most unconjugated verbs. Haben is pronounced with a syllabic n (or m, depending on your accent), for example.
The difference is basically in length. A syllabic consonant is shorter than even a short vowel sound, and which vowel it uses depends on the language. It’s a schwa in English because that’s basically our default vowel, as you pointed out, but not every language uses a schwa as the syllabic consonant carrier: Serbo-Croatian uses [u].
I’m also autistic and also don’t really feel anger. I feel disappointed and/or frustrated with how people act, and I can feel a complete lack of goodwill towards people (not my baseline, I generally want to help people if I can). There are certainly people who deserve negative consequences for their actions and I don’t feel any compassion for Assad, for example. I probably wouldn’t piss on him if he were on fire, but I don’t feel angry with him (I might if I were Syrian and/or had more experience with the effects of his actions).
In my personal life, I don’t have any exes that I’m angry with (and I have some awful exes), it’s either confused, afraid of, pitying, neutral or positive.
Though tbh, I’m not sure if I just don’t recognize anger but do feel it. A coworker was sketchy about a tip we should have shared the other day, and I felt that it was wrong she pretended she hadn’t gotten a tip, and sad for her that she’d be deceptive about €0,65, but I wasn’t angry.
I do feel spiteful sometimes, which has got to be similar, but the only way I really express that is being extra polite to someone who’s being a dick so they feel guilty. It feels to me like I do that because I want them to be less rude in the future and I want to help induce the natural consequence of guilt that comes along with rudeness, but that could also just be my rationalizing it.