Hennahead I know exactly what you mean and how you feel, without having your problem. However, I am dyspraxic. I have poor fine motor control and not good balance. I can ride a bike, but it is hard work keeping my balance, and when walking every so often I trip over and fall, maybe once or twice a year.
Now years of practic mean that I know how to fall and am up and on my feet and continuing on my way in less than a minute, but people rush up to me and fuss around me and one of the reasons I get up so fast is in order to be on my feet and walkig away from people before they reach me, so that they can see i am OK.
I think in dealing with this, it is a question of finding a balance that enables you to keep command of the situation, while not being rude to people. I will usually say firmly and in a clear strong voice, 'Thank you, I do not any help. I am used to this happening'.
The other thing to remember is that the experience is only humiliating if you let it be humiliating I have experience of people trying to humiliate me, but I have always refused to co-operate by acting or thinking of myself as being humiliated. You need to do the same. and being hurt and angry is something else you have control over as well.
Take a deep breath when these occaasions arise, take control of the situation, thank people graciously and then either accept the help or say, 'thank you, I am best left to sort myself out.
Control of the situation and how you respond is entorely in your hands. Do a bit of role play in your mind at home.
Many of the things you mention, probably have more to do with your age than your disability. Sorry about that,but being patronised and it being assumed that one is incapable of dealing with modern technology is one of the burdens age places upon us.