Adding pool member (with same IP different ports) to multiple pools

Hi kristine_v , 
you can add it using GUI without any impact or service intrruption. 
I do not know what is the PGA conditions " less than 1 , 2 ... " but I see that you’ll give it a lower priority score so I think you’re going to make a redundancy on pool member level. 

Anyway , you can configure it with the same way that you configured "App_01:100 and App_02:100" 
but I Curious with your setup , why do you want to attach same pool " which contains 3 members " to all of these Virtual servers ( VS_110 , VS_120 .... ) as I see that you will get the same result when browsing any of them ?