Help understanding SPI settings from datasheet

I'm trying to understand how to setup SPI communication with a Ti ADS8698 from the datasheet .
I'm fairly new to SPI so I'd be grateful if somebody could help me find the right configuration for SPISettings

clock rating: p.10 gives a serial clock frequency of 18MHz so I suppose I should use 18000000 in SPISettings, but the person working on the project before me was using 10000 so I'm confused
data shift: p.36 has an example of data acquisition, and I'm guessing the paragraph Event 3 says it's MSBFIRST
SPI Mode: The SPI library reference mentions clock polarity and clock phase. The data seems to be shifted on the falling edge, and SPI_MODE1 seems to work, but other than that I'm having a hard time connecting these definitions to the contents of the datasheet.

Could anyone help me understand?

18MHz is the maximum frequency you can use with this chip. You shouldn't use the maximum frequency except if you really need to do so.
On an AVR Arduino (you didn't tell us what Arduino you use so we must assume you use the UNO) you shouldn't use frequencies higher than 4MHz, if you chip is on a breadboard stay below 1MHz.

Yes, the chip uses MSBFIRST.

Correct, the chip uses SPI mode 1, clearly visible in figure 1 on page 10.

Thanks for the tip on the frequency. I am in fact using a UNO, and the Ti chip is on a PCB with screw type connectors.

I'm not sure I fully understand how to get all the info from the diagram. The arrow on SCLK indicates the falling edge for the clock samples, is that right? The clock polarity on the other hand is not so clear to me...

That is similar to a breadboard setup.

Correct.

The diagram starts with SCKL low, so that signal idles low.