Even if you still have a couple of weeks on your current stamp, do a border bounce just before the expiry date of the 6th of September, that will get you the maximum time on that visa, depending on when you first enter Thailand you can usually get between 8 and 9 months out of an METV.
Have you seen the native farang on YouTube?? he has lived in the UK for 20 years, and has recently moved back to Thailand, his girlfriend is a British woman, I think he had to get a visa until everything was sorted out, he would probably give you advice if you made contact.
I've heard rumours of people saying it's hit and miss, with bus and train tickets, to prove onward travel, because they want to see a ticket that shows a destination in another country, any train or bus ticket is just a ticket to the border, it's not a ticket that transports you across the border like a flight does, that's why they seem to much prefer you to show a flight, that's my understanding of the situation anyway.
Forget them "fake" onward ticket sites, if you're worried just book a cheap flight ticket to a neighbouring country, that exits before the time finishes that you will be stamped in for, the best way is to just try to check in first, if you have a problem, just step away from the counter and do it there and then, and show it to the airline staff.
the advice I was given, if you're persuaded into buying the insurance to open the account, there is a cooling off period, usually 14 days, just cancel it, when I opened an account, I just declined their offer, but I did use an agent, and that does make it a lot easier.