Correct me if I am wrong.  It seems that if using the WW, I trade a pitcher with 100 innings which he has used 25 prior to the trade, for a pitcher that has 50 innings, do I get the full 50 or just 75% of 50.  Same with hitters and plate apperances.  If this is true in some form, I would like to suggest a column that will let us know how many innings or AB that we get with the trade.

In other words, the prior playing time of both  the player you have just waived and that of the one you just picked up on waivers don't matter. Only the proportional innings or PA with respect  to the season itself in course, as contrarian23 has explained.