ASA Slow pitch - Subs and batting order

Question
Our league is basically goverened by ASA rules, with some tweaking.  We have an "unlimited" sub rule, but our batting order is limited to 12 batters only (1 thru 10 + DH + Extra Hitter).  My team will regularly have more than 12 players on game day, probably 16-18.  My question is how switching who is in and who is out effects the batting order.

We are home team.  Players A is a starter and Player X is on the bench.  After batting in Bot of 2nd Inning, I want to switch A with X.  Player A was batting #9 and did NOT get to bat yet.  X enters the game in the field in the Top of 3rd thus taking over A's batting positions(#9). Now in Bot of 3rd, X gets to bat instead of A.  Correct?
Now Top of 4th, I put Player A back into the field.  Do I need to take out Player X or can X stay in the field at another position? Or must X come out because of X and A having shared the same #9 batting spot?  Can X be sub'd in for Player C, and take Player C's batting spot instead?

I am trying to figure how to get everyone a good amount of playing time, and would like to just have an "odd innning" lineup and an "even inning" lineup, but guys will get skipped in batting this way, i just know it. Is it better to keep a lineup for Inning 1&2, then switch everyone who needs switching for inning 3-5, and then put the starters back in for 6&7?

Answer
Hi Brian,

A starter and their sub or a sub for the sub can never be in the game at the same time.

A starter who leaves the game can only re-enter in their original batting position.  Same for a sub who enters and then leaves.  They can only re-enter in the batting position they originally subbed in.

Players A is a starter and Player X is on the bench.  After batting in Bot of 2nd Inning, I want to switch A with X.  Player A was batting #9 and did NOT get to bat yet.  X enters the game in the field in the Top of 3rd thus taking over A's batting positions(#9). Now in Bot of 3rd, X gets to bat instead of A.  Correct?

correct

Now Top of 4th, I put Player A back into the field.  Do I need to take out Player X or can X stay in the field at another position?

X must leave the game, they can re-enter once.

Can X be sub'd in for Player C, and take Player C's batting spot instead?
No

I am trying to figure how to get everyone a good amount of playing time,
Good luck, sorry i can't help with that

Mark