Regarding RN4020 and MSP430 interface
MCU Interface with RN4020

You need to connect your(MSP430) UART RX and TX to the TX and RX of the BLE RN4020. Make sure the order is as I mentioned above.
Let me explain some further steps,
Refer to page 88 of RN4020 User Guide.
It shows the correct way to define a private service after the first few initializations that you mentioned. You will need these services to communicate with the RN4020.
Once the service is set up and device is discoverable you will be able to see data that is sent via any BLE trasmitter to your RN4020 module on the RX line of the MCU in your case MSP430.
Also as far as I could read from the documentation, CMD pulled low will allow it do me in MLDP/Data Service mode.
Follow the link to see the initializations I did with my RN4020 module to send data from an Android phone to a private service that I created:
https://github.com/sekale/ECE477/blob/master/ECE477_Team08/ECE477_Team08/src/BLE.h