I think no one knows for sure, but in my experience when they are not botting at the same time and they have not interacted with each other they wont get chainbanned.
But if I was you, if you care about the accounts just buy another proxy just to play it safe
Doesn't really matter, as long as you buy em from a 'normal supplier' and not a company who sells them specifically for runescape purposes (chance of them being flagged is higher)
Well it does, but it is still a very bad idea lol. A VPN is shared by many people, and thus your IP is probably already flagged.
You should buy dedicated private proxies, so that you are the only one using them. Costs only like a dollar each
You can also download the file on your computer and then transfer it to your VPS via USB mode. There is an option that your windows VPS detects any inserted USB sticks on your own pc, which comes in handy quite alot
EDIT:
You can also transfer files easily via FTP if I recall correctly