1. It will not display in full screen as this is by design. I do not remember which bios update made this change.
2. Have you set the boot order in the bios? What bios rev do you have? You can get the latest here: https://downloadcenter.intel.com/download/25193/BIOS-Update-KLZ8711D-86A- Download BIOS Update [KLZ8711D.86A]
I cannot help you much as I am not with my DZ87KLT.
Regarding the first issue, yes, this is absolutely true. The version of Visual BIOS implemented for Kinsley was designed for a fixed 1024x768 display. When it was discovered that TVs were being introduced that would not support the 1024x768 display resolution (causing folks to not be able to enter - or, more accurately, not be able to see - Visual BIOS), a workaround was implemented that output Visual BIOS' display in a 1024x768 pixel window in the center of the screen. Depending upon the maximum resolution of your monitor (or TV), the Visual BIOS display may appear small. This is not going to be fixed.
Regarding the second issue, I did not see what you are seeing. When I did nothing but enable (checked) Network Boot, it did indeed get invoked on the subsequent reboot. When I went back into Visual BIOS and moved its entry to the end (bottom) of the boot order list, however, it was never invoked again (and it booted properly from my mSATA SSD). Bottom line, this meets documented behavior expectations.
I would add that, if the SSD/HDDs present do not contain a valid boot image for an O/S (Windows or otherwise), Network Boot, if enabled, will always be invoked.