I think the answer to your first question is that the Trafico will not send to an address outside Spain. They will send to the hire company and the courts will take the view that Trafico have done all they reasonably can to notify you. The hire company are probably obliged to forward to the address you gave them. So everything is in order as far as Spanish courts are concerned.
2) It will have been sent recorded delivery to your only known Spanish address - the hire company.
3) Nice to see that you haven't lost your sense of humour over this. Not a snowflake's chance. The law says it's your fault, not the hire company's. And it wasn't the hire company that went the wrong way down the one-way street or whatever. That was you. And you are guilty until you can prove that you are innocent as Trafico have said you're guilty and the word of Trafico or the Guardia is the word of God. The court will believe whatever they say and you have the burden of proof shifted to you.
4) You will miss visiting a beautiful country full of beautiful people (and lots of Spaniards too) but otherwise nothing much is going to happen. They certainly won't come after you in the UK and you're probably safe going back to Spain. The only way you might be at risk is if you try to hire a car and give the same details (NIE, passport, driving licence number) as before.
As I am sure you already know, the law and justice are two completely different things :-(