1--this is not a standard rib, but a variation of the brioche stitch.
the brioche stitch (k1b) is OFTEN (MOST OFTEN) worked by
Knitting into stitch below (which causes upper stitch to unravel (and become a YO) and lower stitch (the one you knit into to stretch and become a slipped stitch)
the method you are using (YO + slip stitch in row A, Knit Yo +slip stitch together in row B creates the same effect!
2--when decreasing in ribbing, you'll always have to pick a 'break point' --a place where the ribbing breaks pattern
in this case, its after 3 stitches have been worked.
so it will look like this:
VvVvVvVvVvVvVvVvV (no decreases yet
VvV (bold=decrease..note 2 K's in together_
VvVVvVvVvVvVVvV (no decrease this row)
VvV.....(now decrease is in P--and ribbing patterns is established again.. (next decrease will once again have 2 Knits next to each other..
here is sort of how it looks.
(this is the crown of hat (not a sweater) and its standard ribbing (not brioche!) and its 2 X 2 ribbing.. but look at hat.. in 2 rows (rounds) there are actually 6 knits in a group! but it still looks like 2 X 2 ribbing.. (with a main RIB)
your Main rib will be in the seam (underarm or in shoulder of raglan --and isn't nice looking?
Look at the image of your sweater i bet it has a nice 'strong line' at the underarm (or in shoulder line of raglan)