2014 BMW 320i (F30) completely dead - can’t access trunk, no electrical power, no way to check battery/fuses

Looking for some advice before I start tearing things apart.

Vehicle is a 2014 BMW 320i (F30, N20).

A few days ago it developed a P0171 (System Too Lean) code along with a whistling/hissing noise that seemed to be coming from the top rear of the engine. I was planning to smoke test it.

Yesterday the car started and drove normally. I parked it, came back later, and now it is essentially dead.

Symptoms:

• No dashboard lights
• No interior lights
• No central locking
• No trunk release
• No crank
• Pressing the Start button does nothing
• Headlight switch illumination and Start button illumination are present, but no instrument cluster lights
• Jump pack connected to the under-hood jump terminals makes no difference
• No clicking, no cranking, no response

Complication:

• Battery is in the trunk
• Rear seats are fixed (do not fold)
• No ski pass-through
• No external trunk key cylinder
• Electronic trunk release doesn’t work
• I currently have no way to access the battery or rear fuse panel

Questions:

1. Is there a manual way to access the trunk on an F30 with fixed rear seats and no key cylinder?
2. Has anyone seen an F30 lose almost all electrical power while still having a few illuminated switches?
3. What would you check next before calling for a tow?

Any help would be appreciated. Right now I’m stuck because the most likely failure points are in the trunk and I can’t get to them.