Here's how I ended up interperting the "decrease 1 stitch at each end on every alternating 3rd and 4th row 3 times":
Row 1: knit, Row 2: purl, Row 3: knit dec 1st and last st.
Row 1: purl, Row 2: knit, Row 3: purl, Row 4: knit dec 1st and last st.
Row 1: purl, Row 2: knit, Row 3: purl dec 1st and last st.
I had left out previously, that, according to the stitch counts I had, only 6 stitched needed to be decreased for this section. However, it never said anything about the number of rows needed for each repeat or how many rows you were to end up with. So, I put a lifeline in and figured that I would rip back if the sleeve did not fit into the body properly. I am sooooo happy that it did though!!! it fit perfectly.