To be honest, I am surprised that your co-founder dares to do this before you guys go live... Everyone knows you do NOT mess with the tech co-founder, especially not pre-launch. To echo the first comment, it sounds like a toxic environment. You gotta get yourself outta there!
Don't fret, my friend, It sounds like you are in a very good position to negotiate. The CEO/other members of the team do NOT want a Facebook on their hands, so it's likely that they'd want to work this out either now or later. I am not familiar with Canadian law at all, so unfortunately, I can't help you with that. But if it's anything like US law, all of those informal pieces of "evidence" would be enough to prove your equity. Remember- you have a lot of bargaining chips. You can very strategically negotiate your way to the amount of equity you deserve. Is your company incorporated in Canada or the US?
I am an IP/startup lawyer and I know the startup world intimately, having worked for/in one. You might want to arrange a deal with the other members of the startup to buy you out, since you no longer want to be part of the team.
Also, Do you have any emails/voicemails/texts memorializing your 5% equity? The reason I ask is bc sometimes formal written agreements aren't necessary in some cases.
From an IP standpoint, if your initial agreement did NOT give all the ownership of the code you've written to the company, then you ARE the rightful owner of the code, doesn't matter how much you were paid/not paid.