It’s hard when people tell you things are “normal” when you feel like you’re struggling. Self soothing at that age isn’t really a usual response to tantrums but may be how he learned to cope very early on - he literally may have no idea how to accept sooothing when he feels so overwhelmed. And yes, I can really understand feeling rejected.
I found the concepts of therapeutic parenting really worked with one of my children and really didn’t for the other. She was confused about where the boundaries lay, couldn’t work our natural consequences and was very used to having to cope with strong feelings on her own so didn’t know how to ask for help or care.
It sounds like you’re doing a great job, even if it feels like you’re not. The return to routine after holidays throws kids out at the best of times but for a little one for whom routine feels safe, it’s a bigger challenge. Something I found helped was almost constantly chatting about the plan for the day, the week etc. So “today is nursery and we’ll have breakfast, get dressed, mummy will come and get you at x and we’ll do y this afternoon. Lather, rinse repeat.
If he really doesn’t want you near if he’s having a tantrum, and you’re sure he’s physically safe, be with him but not touching, maybe start playing with a favourite toy and when he starts to calm invite him to join in. Theraplay activities can be good for this because they build connection again.
Most of all, you’re human and your little one needs a human relationship with him, you can’t be therapeutic 24/7. Even trained, experienced therapists aren’t therapeutic 24/7, in all of their relationships so please stop beating yourself up. As long as your intention is about building relationship, and you remember the principles of PACE, and try to put them into practice when you can you’ll be good enough. Which is what he needs.
Do get some time away to do grown up human things. My sister gave me a Costa card too in the early days and I used it for coffee and cake and time to just sit, read and rest. The time away was essential for my health and well-being.