MacOS – Macbook pro, black screen with chime only after using Casper/JAM

If you have your original discs load up the Applications Install disc and run the Apple Hardware Test from there. Look for memory faults. I doubt very much you have a firmware "bug", memory failure is much more likely and would explain the unusual hardware behaviour you're experiencing.

I had the same model which I initially bought around 5 years ago, this had the original OS installed (10.5.6). Immediately after purchase I used the install discs to wipe the machine totally clear of the previous owner's setup, no problems encountered during installation.

Everything seemed to generally work ok (one or two occasional random crashes) until I decided to wipe it clean following the retail release of 10.6. After trying (and failing) several times to install 10.6 I decided to substitute the factory 1GB RAM stick with a 512MB stick from another laptop. This time 10.6 installed perfectly, first go. Faulty memory explained the random crashes as well as the installation issues with 10.6. Incidentally, I tried running the machine after installing 10.6 with its original 1GB RAM. It would sometimes boot but was completely unpredictable - single user mode was always accessible though, like your setup.

It honestly seems like you have already tried everything a genius bar would try themselves. However I think I might have some attempts here to help you out.

All boot-up key combinations can be seen from here: https://support.apple.com/en-us/HT201255

1. Remove all connected USB, HDMI, or other plugged in devices including power cable. Try booting again with holding option to select a disk. I recommend doing this after steps 2 + 3, but remove cables first.

2. Lets ensure you are indeed resetting the SMC. This works best without 100% battery, because the light will be orange when charging and the computer is off. While off and the light is orange, hold down shift+control+alt/option and then after holding those three keys hold the power button a moment and release and watch the light change from orange to green to orange again. Volume should also get reset from this. (This can be done without any issues involving firmware password)

3. Clearing NVRAM by holding Command-Option-P-R. NOTE: This will require your firmware password to clear it, but I don't think it will clear with one as I've noticed it doesn't for my MBPr mid 2012. So if you can, remove the firmware password and then try this. But from a command-line terminal the following command will also clear your NVRAM.

Requires Administrator privileges! This is also funky with MacOS Sierra due to new restrictions with their attempts for a new secure system meaning it'll require you to be in safe mode to run it.

sudo nvram boot-args -c

I have more info on boot-arguments if necessary. Just ask.

4. Boot into Internet recovery by holding Command+option+R (Differs from normal recovery because this downloads your original factory release OS recovery rather than using the partition of your current OS on disk.)

5. If it is hardware, lets try Apple's Intel CPU check by holding down 'D' while booting up. This is a hardware test and takes a while.

Let me know how you make out.