Well, for you could use your while loops iteration terminal to do both issues. For the first, decide how many aquisitions you want to have in each file, then, use "quotient and remainder" function under numeric function palette to divide the iteration terminal value by this, then everytime the remainder is zero, change your filename from "filename.*" to "filename-1.*". For the second do the same, with a smaller value, let's say 3, and everytime remainder is zero pass data to your graph, or else.
Hope this helps