F28377S sci_echoback_cpu01 clocking and BAUD issues

Hello there!  I'm having an issue running the sci_echoback_cpu01 example from the ControlSuite repository.  Here's the thing - the example is originally configured for a 9600 BAUD, but actually works at a 4800 BAUD instead.  This got me thinking that the clocking was incorrect.  As per the example code, 

    //
    // SCIA at 9600 baud
    // @LSPCLK = 50 MHz (200 MHz SYSCLK) HBAUD = 0x02 and LBAUD = 0x8B.
	//
	SciaRegs.SCIHBAUD.all    =0x0002;
    SciaRegs.SCILBAUD.all    =0x008B;

	SciaRegs.SCICTL1.all =0x0023;  // Relinquish SCI from Reset

This is with manually setting the LSPCLKDIV to 4 (should be the default), 

   EALLOW;
   ClkCfgRegs.LOSPCP.bit.LSPCLKDIV = 4;
   EDIS;

And manually setting the cpu clock to XTAL as such (default for the program), using the API from usb_dev_serial

   SysCtlClockSet(SYSCTL_OSCSRC_XTAL | SYSCTL_PLL_ENABLE | SYSCTL_IMULT(20) | SYSCTL_SYSDIV(1));

But as per the usb_dev_serial comments,

      SysCtlClockSet(SYSCTL_OSCSRC_XTAL | SYSCTL_PLL_ENABLE | SYSCTL_IMULT(20) | SYSCTL_SYSDIV(2));

should generate a 50MHz clock.

So a few questions:  

1. What's my clock actually running at?  I know the calculation for the clock speed should be XTALSPEED*(IMULT*FMULT)/SYSDIV.  Is the calculation for the BAUD incorrect or is the CPU frequency incorrect?
2. What is the XTAL frequency?  The datasheet says it's between 10 and 20 MHz, but I can't find any indicator on how to change it and actually specify it.
3. How do I set the CPU to 200MHz?  If I change the CPU config as such, I get illegal interrupts,

   SysCtlClockSet(SYSCTL_OSCSRC_XTAL | SYSCTL_PLL_ENABLE | SYSCTL_IMULT(40) | SYSCTL_SYSDIV(1));