Apologies in advance for the lengthy reply here. It may be a little difficult to fight, but until I get some actual case law that says London v. Young is no longer applicable, I'm going to stick with the idea that the law should be on your side. Present everything - the error on the ticket, the lack of disclosure, just like you said in your original post. Your appeal is under section 135 of the Provincial Offences Act. The procedure for it is loosely outlined in section 136, which basically says it is like a "review."
(FYI - Justice is wearing a red sash, he's addressed as "Your Honour" as opposed to "Your Worship." Green sash = JP, "Your Worship.") When you begin, state in some way that you are unable to afford a lawyer so you appreciate their understanding, as you have no formal legal training yourself. Your evidence is straightforward: You received a ticket, did not appear for trial, the ticket was not complete and regular on its face, the Justice of the Peace entered a conviction contrary to the procedure required by section 9.1 of the Provincial Offences Act and against precedent established by London v. Young, City of Barrie v. Porter, City of Sudbury v. Leikermoser, R. v. Monahan and R. v. Montone, and that the ticket should be quashed and a finding of not guilty entered against you. You may be asked why you did not appear for trial.
Have a binder of evidence and your arguments. Study those specific cases and see what you can do with them. R. v. Montone is very similar to your case, except it was for running a red light. Basically you can use transcripts, or any records you can get, to show that the fines were incorrect. The JP cannot amend the certificate without you present. Justice K. Feldman of the Ontario Court of Appeal wrote in the London v. Young case that "the set fine forms part of the basis used by the defendant to decide whether to default."
The other thing to add to your arguments that you already posted is that if the fine is incorrect, you could possibly run into trouble for not completely paying the fine, or you could be ripped off for over-paying. They're supposed to correct it, but given the numerous mistakes already made, that seems unlikely. When someone defaults and does not appear for trial, the state has the obligation to ensure that the paperwork is done correctly. If not, someone could get their licence suspended or get ripped off because of a paperwork error, which is why the fine should be correct and proper and the JP must examine it - as you said. You have now had three different fines given by three different people. How is a layperson supposed to know which one to pay? This is not acceptable, it is a Gong Show, and the only fair remedy is to quash the certificate.
They'll probably argue that you did file for a trial, which is different than not responding, but R. v. Leikermoser says that failure to appear triggers the same provisions as failure to respond.
Anyway... that's what I would do. Keep in mind, though, that I do not have formal legal training. While I have observed quite a few trials, defended myself a couple of times and helped a few friends with theirs, that's the extent of it. I do not pretend that I'm some sort of expert. IF we can confirm that London v. Young is no longer applicable, that changes things... but you still could argue that the whole thing should be quashed because of the administrative errors made by the JP and clerk.
Good luck with it.