Identifying stitch and decrease in pattern

How-to Questions
1

I started a new pattern today, and I got stuck immediately. Can anyone identify the stitch used? It looks like a moss stitch to me but the way it’s worked is pretty different.

It starts to decrease fairly early on, I’m confused about the wording, is it decreasing on each end? Does the pattern account for the decrease which changes the pattern of the stitch. How can I decrease this stitch properly so it doesn’t shift it?

“PATTERN STITCH: Multiple of 4 sts plus 3.
Row 1: K 3, * sl 1, K 3, repeat from * across row.
Row 2: K 3, * bring yarn to front of work and sl 1, throw yarn to back of work, K 3, repeat from * across row.
Row 3: K 1, * sl 1, K 3, repeat from *, ending sl 1, K 1.
Row 4: K 1, * bring yarn to front of work and sl 1, throw yarn to back of work, K 3, repeat from *, ending bring yarn to front of work and sl 1, throw yarn to back of work, K 1.
Repeat these 4 rows for pattern stitch.”

Decrease:

dec 1 st each end of needle every 10th row 12(13) times; every 8th row 3(6) times; every 4th row 13(9) times; every other row 2(3) times and EVERY ROW 20(22) times. Bind off remaining 31(33) sts.

https://freevintageknitting.com/free-jacket-patterns/bernat59/cape-pattern

2

The photo looks like seed stitch but the pattern as written is a slip stitch. I tried the pattern stitch and it looks nice but I can’t say that it looks like the photo. Try it on 15sts or so.
Yes, decrease at each end of the back. That’s 2sts decreased for each decrease row. This isn’t accounted for in the pattern but by the time you get to the first decrease row, you’ll be able to look at the previous rows and make sure that the pattern stays aligned with those rows.