I have a slightly different approach that may not be helpful as it does not use Pulldata request.
I created a select_one field with the name MONITOR that reads a short list from the choices tab with the list_name monitor and name choices of 1YR, 3YR, 5YR, and 10YR
I next have a calculation row with the name nextcalc that has the formula if(${MONITOR}='1YR',date(decimal-date-time(now())+365),if(${MONITOR}='3YR',date(decimal-date-time(now())+1095),if(${MONITOR}='5YR',date(decimal-date-time(now())+1826),date(decimal-date-time(now())+3652))))
I finally have a text field named NEXTINPS to display the Next Inspection Date that is ReadOnly with the formula format-date(${nextcalc}, '%b %d, %Y')
The Previous Inspection Date shown in the screenshot has nothing to do with the Next inspection Date other than to inform the user of the last inspection to help the user determine if the next inspection should be the same time span or if it can be different in the future
I hope this is useful.