DP/Flex situation

Question
I am a high school varsity coach. This is the line-up I start with:

1.  Player A (CF)
2.  Player B (LF)
3.  Player C (SS)
4.  Player D (3B)
5.  Player E (C)
6.  Player F (DP)
7.  Player G (1B)
8.  Player H (2B) - also my back-up pitcher
9.  Player I (RF)
10. Player J (Flex - pitcher)

My question is if my starting pitcher (Player J) is not throwing well.  I would like to move my DP in to play second and move my second baseman over to pitch.  Everyone is still batting in the same order, but I go down to nine on my line-up card.  Is Player J considered to have left the game since she is not on defense, even though the DP did not go in for her? Can I only re-enter the same pitcher (Player J) once?  Thank you for your help.

Answer
Hi Jamie,

B6 (DP) did go in for the Flex because the Flex plays defense and the DP is now playing defense and the Flex is coming out.  "Blue..#F in for #J".  Don't get confused by thinking about where or what position they're playing, that doesn't matter.  The game goes down from 10 to 9 and it is a substitution for the Flex #J.

Yes #J can re-enter once either back at the 10th position or at B6.  
If at B6 the DP leaves the game, it is a sub for #F and the game remains at 9.  #F can re-enter once.  

If in the 10th position, the DP can leave the defense, continue to bat at B6 and it not a sub for #F.  OR.... #J back at 10 leave the DP still playing defense for any player 1 thru 9, who continue to bat in their batting position and are not considered to have left the game.  Both the DP and the Flex in this situation are both playing defense and that is legal.

Mark