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AD9528 jitter question

Hi there,

We are using AD9528 as our clock generator in ulrasound system.

Basic topology is:  Crystal(200MHZ, 100fs jitter rms) ---> AD9528 ----> Clock Fanout Buffer IC(ADCLK854,54fs rms) ----> AFE ADC(may use AD9276).

All LVDS clocks.

Some questions about Jitters of AD9528. 

1. If we use Buffer Mode, Output Additive Jitter is about 140fs. so total rms jitter for AFE ADC clocks should be roots.quare(100*100+140*140+54*54) = 180.3fs rms. Is my perception correct?

2. If we use PLL Mode, OUTPUT 【Absolute】 Time Jitter is about 179fs. For the "Absolut jitter", does is mean , there is no need to consider jitter of Crystal ? Not sure about this.

3. For AFE ADC GND layout, is it necessray to seperate Analog GND and Digital GND, and connect them at one point? Or could we use one complete GND plane? 

4. Any suggestions on CWx16 clocks jitters selection? Also, guidance on layout and routing about CW siganl is appreciated

Thanks very much!