@Petra42 thanks for sharing with us 💐
In terms of my DH he would potentially be similar to yours, on a work trip say, that would be stressful, low autonomy, overwhelming and tiring. Due to alexithymia he might struggle to tell me why (beyond overwhelmed). In the worst case he'd insist he's 'fine' since he's internalised a rule 'you need to be fine when you're with other people'. My DH would get grumpy and then withdraw completely into a shutdown / dissociation. These have previously lasted for months, if he gets close to burnout. That cycle is super lonely!
It sounds like your partner maybe has low social needs and is having them met by you broadly. Is he diagnosed or willing to seek diagnosis? Both of us have benefited hugely from one. Our communication is so much improved.
(The feeling that your partner is another kid was quite a difficult one for me and totally killed adult desire imho. I'm so much happier now I've refused that cater role and DH gets a variety of help from elsewhere. How are you feeling about that?)
(I hope this doesn't come across as rude but many of us on the thread have done some thinking about why we're with 'difficult' people and I wondered if you had a good sense of what mutual benefits you're getting from the relationship? Without wanting to be transactional I think it's healthy to know that).