Hi, just wanted to put my 5 cents in. My DS#1 was a short napper from 3 months old till around 8 months (it started to get gradually better from 7 months). He was falling asleep independently in his crib, and then after 30 or 40 mins would be wide awake in a sec. No matter what I did - playing with A times, helping him to sleep through by putting pressure on his joints, AP him to sleep longer (rocking him to sleep when he would awaken on his 40 mins mark, or letting him sleep on me) - and believe me, I did a LOT of that to avoid OT and night wakings - nothing helped.
So I guess what I am trying to say - hang in there, do not make yourself crazy over this, this is just developmental and will go away on its own.
In the meanwhile, try helping him to sleep through - W2S didn't work for me either, but modified W2S (going in there on 35 mins mark and holding him through the light sleep phase, for about 20 or 25 mins) did - he would sleep through and would continue to sleep for another 30 or 40 mins after I let go. I guess this teaches him to sleep through.
Sending you hugs, it is such a hard and frustrating time (I am also there with DS#2) but it will pass very quickly!