You're doing well so please do cut yourself some slack!
No 2 children are the same, one may thrive with after school clubs to burn energy, another may be exhausted. If you find the clubs aren't making behaviour worse on those days then I wouldn't personally give them up.
Sometimes with a ND child there is an element of trial and error to find what may work. I think it is important to express 'it is not okay to kick' or whatever they have done, either soon after the event quietly and calmly, or once you have taken yourself for a moment.
I try to combat super loud crazy behaviour or shouting/screaming with lowering my volume until I'm whispering. Even if it's sometimes when things are happy and I'm whispering for a bit to offer a nice treat. Just to encourage them subconsciously to quiet/self calm just to be able to hear what you are saying. I find it more soothing for myself to just keep getting more calm and more quiet in this environment too, as it helps me at least feel in control of myself
For a bath you could try different things he may like. Light up toys, bath bombs that change the water colour, bath bombs with a toy in the centre, crackle baff etc. mine would fight off a bath without a bath bomb/crackle baff on offer each time. With them it is not too bad, still some objection to the initial hair wash, but he gets to put the bath bomb/other in as soon as it's done, so it's more manageable. In particular he likes bath bombs with little toys in the centre and you can't get multi packs (may not work for yours - just a suggestion, there may be something else you could do)
Try to list 3 clear priorities for yourself to break it down and feel manageable. For some people it may help to write these in a book and note progress/things to remember that worked/didn't
Managing daily behaviour
Getting support whilst not diagnosed
Getting a diagnoses
For the getting a diagnoses part - don't give up. Compartmentalise it by booking an appointment with the school (simply ask for a meeting with the school teacher and SENCO) and the GP, then forget them until the day. Once the day has come say everything you are saying here. Let them know it is not manageable and you need a referral, that a referral will generally put you on a long waiting list and you'd certainly remove if things change, but that you cannot continue without support and help. If they reject, book another appointment and repeat.
In terms of help and support whilst not diagnosed
Please do look online at support in your local county. There are often things like support groups where parents speak on zoom/other to each other. Sessions with a support worker to give guidance on dealing with specific struggles (sleep/feed/school/behaviour etc). It helps to not feel alone, and to continue getting ideas for managing the behaviour as you go along. After a diagnoses you would be given leaflets listing these support sites/contacts, but I think they all let you sign up pre diagnoses.
www.scope.org.uk/advice-and-support/find-support-services-before-child-diagnosed/#:~:text=Contact%20your%20local%20authority%20to,support%20that%20your%20child%20needs.
www.autism.org.uk/autism-services-directory
www.youngminds.org.uk/parent/parents-a-z-mental-health-guide/adhd/#Usefulhelplinesandwebsites