Recreate the ISO image, this time in Rufus, under "partition scheme and target system type" i chose the last option "GPT for EFI..
I don't know Rufus, I always burn my boot sticks with Mint's Image Writer (maybe you should do that, boot your live Mint Usb and use Image Writer to prepare a second Usb drive, then use this for install)
OK so i have booted to Linux using the USB, then searched for Image Writer in Menu and there came up USB image Writer.
I used that to write the Linux Mint 18.2 to a USB
There was no settings at all, just a plain tool with "load the image" and Write...
Should i reinstall Mint using this USB ?