Uhh this is one money hungry game indeed, it's like a bottomless pit for your cash.
1.They most likely use a list of known proxies, did you try just googling for some proxy IPs, newer ones, or less known ones beyond the first pages of results?
You can try to access some sites that detect your IP and proxies, and see if it detects you are using a proxy.
There are other ways they can detect proxies, but this is the most likely one.