Good day everyone. Old guy (70) looking to relive my youth.

I have taken on a project (Chevy 1966 C10 short-bed fleet side. Had an 1968 L78 396ci from '68 Chevelle SS rebuilt to stuff underhood along with rebuilt TH400 trans and 3:73 gears. Originally had a new Holley Ultra double pumper (650cfm) installed, but could not get it dialed in. So I returned it and bought the MSD Atomic. Pretty straight forward on install, and as promised (if ya follow the directions) it started up on first try. But the hard part isn't installing it's tweaking the system (and that's where I'm struggling). The distributor and timing I had done at a shop by Master Mechanic. So I'm looking for some input numbers to get a somewhat decent base to start from. I don't have much knowledge on the Atomic TBI or any fuel injection system for that matter. I have read about half of the threads on this forum, so naturally I now have mental confusion. The engine idles rough/drops out and stalls- backfires through exhaust or TB and doesn't seem to have a lot of power on high end. it does run better at higher RPM. But I haven't been pushed back in my seat yet.

Shown below is the Engine data and current handheld input data. Engine 396 bored +.030" - Comp Cam #11-600-8, LSA 107°, @ 0.50" - Intake 227° - Exhaust 241°, Edelbrock Performance RPM dual-plane intake with 1" spacer plate- compression was lowered on rebuild from 11.0-1 to 10.5-1- Hedman 2 1/2" full length headers no X-pipe, Flowmaster muffler short exhaust out in front of rear tires. WBO2 sensor is in left hand collector box. Engine wasn't dynoed so no idea of HP or torque. But I believe there's plenty of each. Ignition system is all new up to date MSD with phased rotor.

Initial settings:
396 ci
cylinders- 8
cam- performance
fuel pump- non-PWM (not in tank) with regulator and return line.
air pump- NO
idle target- 850
rev limit- 6500
timing- enabled

Advance settings:
AF targets- idle-14.0 cruise-14.0 WOT-12.8
Nitro- off
Boost- 10.0
Pump squirt-25%
Power Valve- 15%
Nitro- Disabled

Idle RPM-950
Total RPM- 2200
Idle advance- 12.0
Total advance- 30.0
Vacuum advance- 10.0
Vacuum type- un-ported
Nitros rtn- off
Boost rtn- 0
Fuel pressure- 43
IAC neutral- 0
IAC in gear- 0

So there ya have it. Any and all suggestions will be read and hopefully lead me to a good running engine. I'm Looking for PERFORMANCE not MPG. Thanks in advance.