I loaded up tdm2 that you provided above, ran it on my hardware, and captured some data with my oscilloscope. Interestingly, with the Parameter1 setting of 6.25MHz provided in tdm2 SCK (DIO25) outputs at 3.125MHz as shown in the first screen shot.
If I increase the bus frequency of Parameter1 to 12.5MHz then SCK outputs at 6.25MHz, however, if I leave the sample size in the bus settings at 128, Select (DIO24) outputs at 96kHz. In screen shot below Parameter1 is set to 12.5MHz and I have edited the bus increasing the sample size to 256. I now get Select outputting at 48kHz but SCK is zero half the time.
What am I missing in the configuration settings that I need to set to get SCK to output continuously?