It sound like the coefficient of friction of the B3 reverse clutches and the B2 band is too high. To aggressive.

Check the transmission fluid level and condition does it have a milky or strawberry color. If it does, the transmission is contaminated with coolant from the radiator. This type of failure if not caught early needs a rebuilt transmission and radiator.
Dirty and worn transmission fluid can also cause the condition you describe.

If there is no coolant contaminated and the fluid looks dirty and worn, no Burnt odor.

Do a transmission service, filter and drain the torque converter. Refill using MB fluid # 001 989 07 03. Drive the car for 200miles, which should be enough time for the oil to soak into the B2 band and B3 clutches.

If you still have the harsh engagement, the transmission needs rebuilding, change the B2 and B1 band also the use the updated B3 green clutches.

Engine stalling going into gear,

Look for corroded or loose wires in the neutral safety switch on the transmission. It can also be engine relayed; I am a transmission tech, so I could not tell you were to look.