Need clarification on your hardware configuration.
Laptop has DP, right?
Monitor is HDMI only?
You're using a DP->HDMI cable to connect the HDMI monitor to the DP port on your laptop?
What is the make/model of the monitor?
Notes/questions:
- your ioreg shows the serial port enabled (as per post #1, should be disabled)
- it also shows Firewire enabled (as per post #1, should be disabled)
- you might try removing Lilu.kext + IntelGraphicsFixup.kext (they are not needed for your hardware, and should do nothing, but maybe that is not the case)
- your ioreg shows no external monitor connected (attach ioreg with external monitor connected)
- what happens with DP->DP?
- is BIOS up-to-date
- you have Sierra, but why is it not 10.12.6?
From where did you download macOS?
On what hardware did you create your USB installer?