I have been reading your description of your woes with an increasing sense of disbelief. I am not one to use labels but the term snowflake comes to mind. Bearing in mind I have sons of your age....
1. To use an adjustable spanner vise grip etc is an insult to mechanical engineering, they always rip material from the nut and make it round. Spanner sets and ring spanners were developed for a reason.
2. Aluminium does not rust. Steel does.
3. It is very normal to have different diameter nuts and shafts on rear wheels than on front wheels. The back wheel has to withstand torque while the front one just need to rotate. Newton s laws etc.
4. An electric bicycle comprises three elements each of approx equal cost. A frame , a motor and a battery. Now if the entire bike cost 1000 then you have the mechanicals of a 300 quid machine.
5. There is only one test that any court would use.. was the product of merchantability quality and did it give good service?. To use a product for a year, and it is still operational , means it passed that test. User satisfaction or dissatisfaction is not a factor, ...
I could go on but will stop here. You suggested you weren't looking for sympathy, that's good...