I've had severe demand avoidance my whole life. If people interrupt me or keep trying to get my attention without considerable breaks, I get quite overwhelmed. I mean that I can easily go into a complete meltdown if someone continues to interrupt me after I've asked them to please stop, even if their interruption is seemingly helpful and selfless.
I seriously broke up with a girl that loved the hell out of me because she just couldn't stop interrupting me when I was engaged in something. I completely blocked another friend I had for ~17 years after going on an international trip with him because after asking him repeatedly to please stop blurting out every single idea he has, to save them until I seem like I want to hear it. Nope, he just couldn't do that. It is just completely unbearable for me, and after leaving the trip on my own earlier than planned, I blocked all opportunities for him to contact me. I would be happy to never hear from or of him ever again. That's how much I cannot tolerate demands.
Aside from that, the best part of my day is when I go to bed to lie down for the night. It is my safe place where I know no one will interrupt me because everyone is asleep. This happens even if I live alone.
Unfortunately, the way this plays out is that I end up isolating myself and have pretty bad sleep issues since I basically stay in bed awake for hours at night. It's like my body wakes up once I hit the bed, which is terrible for sleep hygiene. Last night, I went to best at midnight and didn't fall asleep until 5am, so I'm exhausted-tired today.
I'm working with a therapist to develop a social circle that is healthier for me, so that's on the horizon...hopefully. When I review my life, my favorite relationships are ones where I just co-exist with someone in the same space without much direct verbal interaction. I enjoy touch and sharing, but not if they talk a lot. And if they do talk a lot, I prefer if they keep the talking consolidated rather than spreading it out throughout the day. I can tolerate 2 hour conversations wayyy better than 6 hours of talking for 5 mins repeatedly.
Any other suggestions on how to manage this?
I'm kinda frowning at the thought that you requiring time to yourself and taking care of yourself is avoiding demands. If my therapist told me that I'd rip him a new one. Thankfully he doesn't and actually encourages me to remove myself from unhealthy situations.
My social battery isn't endless. My processing ability isn't endless. I recharge both by spending time alone in my thoughts and hopefully getting into a flow state with whatever I'm doing.
I'm lucky enough that I have a job where that happens - I'm partially able to offset the social and mental cost of a job by simply working. But other than that I allow myself to not be productive.
My awesome therapist once prescribed me to get bored. Sit on the couch, stare out the window and try not to do anything. My brain needs that time to process everything happening during the day. Scrolling the web, comics, news that interest me? Also helping to process and get lost in a flow state.
Once I started allowing myself that, I fell asleep much better, because the input throughout the day gets processed througout the day and not at night. If you always keep busy, try to always be productive, the whole input waiting to be processed builds up like water behind a dam. Once you lay down, the dam breaks and you can't stop. It's not a bad habit to break. It's just a necessity for your brain to do.
If you're anything like me, the only thing you're doing "wrong" is not creating little islands of boredom and flow. If people refuse to accept that, they are the problem. They are crossing boundaries without a second thought. They may think they are helpful but they are not. To me it sounds like you are having your best interest in mind and acting on it despite this weird feeling of "but they love me, I should be grateful".
Love is about a lot of things, and respect is a big one. If boundaries are ignored, these people are acting toxic. I know this feels unhelpful, because you want human connection, but imho these people most likely took more out of you than they gave you. Maybe your friend has his own issues that make him not able to shut up, but it can't be you who pays the price. Maybe that girl thought you need someone to take care of you and who knows better than you and guide you through life, and that's why she nagged.
Long story short: no matter the intention, not everyone who cares about you will be actually helpful. Not everything is your fault. Keep doing you, identify your needs, communicate them (it sounds like you already did that, which is huge) and then enforce them.
From what you mentioned, I actually think you're doing great. Took me years of therapy to get to that point.