Major Issue!! Electrical?

[obeeone]

I am helping a friend work on his 2006 530xi which seems to have some major electrical and running issues.
The problem started with stalling as he would come to a stop, but then he could restart and drive again. The stalling then continued to get more frequent until it wouldn't stay running for long. He was told that he needed a new DME and had a new/used one cloned to his and installed which didn't change a thing. He was then told it was a crank sensor which he installed, but again didn't change anything. He was then told it could be a battery so he installed a new one, which again didn't change a thing. At that point he gave up and the car sat for about 6 months.
He went to try and get things up and running and the new battery was dead so he charged it, but then noticed his Idrive screen flickering for a bit until it went completely dead. At this point he has no Idrive or radio etc. He did try the eject power button reset of course, but nothing happened.
He has since had the new battery warrantied and replaced so that is again brand new.
Now the strange thing is the fuel pump will continue to prime on/off with the key on, but not starting. It just keeps cycling about every 5-10 seconds continuously. Also, you can hear some other electronics cycling about the same frequency.
One other thing I noticed using Bimmerlink and actively monitoring the sensor values is the car seems to loose communication once it starts to stumble before it dies. I can kind of keep it idling by fluctuating the gas pedal, but all sensor values loose communication. This happens as soon as the engine stumbles.
Right now I am looking for any ideas of what to check and possible issues?
EKP module?
Relays for DME?
I am reading through the Power Management and Voltage Supply and Bus Systems documentation to better understand how to track this down, but I am open to any and all suggestions.

Edit, Forgot to add that with the key in and ignition on the check engine light continuously flashes and the info on the dash cycles through the 4x4, sos, low tire warning etc.

TIA.