Take the dang speed idle setting off of the transfer slot( the throttle plates need to be below that slot ) and make it idle on the idle circuit only
There have been many bad myths posted on here by people who took a short cut instead of fixing the real issues with the motors and carb tuning The reason the idle mixture screws are not working is your motor is not idling on the idle circuit, it has all the fuel it needs now coming from the transfer circuits
Start over with both idle speed screws unscrew away from the throttle linkage and then turn both screws in one full turn and see if it will idle in neutral and in gear, if it won't add one full turn on both idle speed screws until it does, it shouldn't drop more than 300(100 to 200 RPM is the best) RPM from in neutral going into gear
Once you have it there then slowly try tightening up the (leaning it down) idle mixture screws 1/4 turn at a time, one at a time and then do the other three.
You should be able to make the motor die from being to lean by adjusting one mixture screw too lean for the motor to idle on
BTW, what do you mean with the "latest timing curve"? What does it idle at and where, what, RPM, and how much total timing does it have a what RPM also? I have no clue on the new gen 3 hemi ignition parts or how they are set up
Good luck, let us know your results