Progress for sure.
When in TX mode your IRQ0 says you have crossed the FIFO Input threshold and IRQ1 says FIFOFull.

Why don't you try changing your definition of IRQ1 for TX (IRQ1TX) from 0 = FIFOFULL (default) to 1 = TXDONE. This is your RF_Init_Values[13] value.
Then in the Send_Packet: routine after changing the mode to RF_TRANSMITTER, instead of a hard pause 5, use a loop to test for IRQ1 to go high (TXDONE).
This way you can explicitly test for the Transmitter to complete.