1. your comparator can either drive a chain of tapered inverter- also known as tapered buffer. That generally drives bigger loads with improvement in delay. If you wish to drive even larger load- try reading about Hidh Drive Buffer- i drove 1nF cap using that. But in your case- I guess tapered buffer should help you..
2. for jitter analysis- export the output of transient response (you will see it in .csv forma) into excel sheet and then you can simply calculate Absolute, Cycle to cycle and periodic jitters in excel.
3. even i am confused- but you can use switches and control switched using mux. A switch is either on or off. So that way Mux can control it and on the input of switches apply analog signals. not sure though- but worth trying.
Regards,