Okay, rows 2 and 4 have to be worked in reverse, not just changing the purls to knits and knits to purls.
So row 2 would be p2, k1 yo, k1 and row 4 is p2, k3.
Now, to decrease the sts, leave out the yo on a row 2, and then you'd have just k2, p2. Then the next dec row, p2tog every other or every 3rd p2 rib, work a plain row, then do the other p2togs where you still have 2 purls. Work a row plain (k2, p1) and k2tog every other or every 3rd knit rib, and do a plain row, then finish with k2tog in the other knit ribs. Then you can k2tog on the last row. Try that and see how it works.