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#21
Have you called the PC's tech support which is included for the first year and should be able to tell you how Win7 can be installed. If they say Win7 is not supported (an old tired line since we've gotten it installed on every other make/model except this one) and don't have a convincing reason, try to probe them for how to install any other OS which may reveal the setting change needed, or lack of one.
By now we've dealt with just about every make/model here and UEFI. This remains the only one I can recall we weren't able to help install to UEFI or at least Bypass UEFI to Install WIn7.
Since we quite rigorously went through the settings to some annoyance by the OP, which is nearly impossible to do and not attempted anywhere else on the web that I've seen in such detail, let's assume yours are the exact same as you say and you also have checked for any recent UEFI firmware update which are quite frequent on these BIOS' for exactly this reason.
One question that was not answered was when I asked about the backup fail-safe method that has always worked when UEFI won't cooperate in the past, which is to Bypass UEFI to Install WIn7. The OP asked how he can do this when he can't even reach the install screen, yet the steps can in fact be completed without the WIn7 installer booting by using Partition Wizard to Wipe Disk - Video Help. which clears all boot code and allows converting the drive to MBR: How to Convert MBR Disk to GPT Disk | MiniTool Partition Wizard Tutorial.
The may force the installer to boot as a Legacy device with the CSM setting in BIOS, and Secure Boot disabled. If not you can try booting disk or stick as a UEFI device to see if it will install to UEFI. Either way you'll need to wipe the drive first to convert over to the other GPT/MBR format.
Be sure to make your Recovery Disks so you have a path back to Windows 8.
As always we will stick with this until Win7 is successfully installed as we've done for tens of thousands of others with a nearly perfect record of success. Had the OP continued to work with us we would have tried at even more things that have worked in the past, including and up to contacting the maker to help determine what the exact problem is - which hopefully you can now continue to do if we don't hear back from OP.