I'm 5'4 + and wear a size 2/4...I shop JCrew regularly. They have S (short ) and R (regular) sizes for the majority of their pants. 8 out of 10 pairs in my closet are JCrew (cords, chinos, slacks, etc) I shop their sale and factory sites to save $$$.

I also have AG, Citizens, and Sevens, but wait for sale days to scoop those up.

My other favorite place to shop is Nordstroms, their Halogen line is nice for work and the prices are reasonable.

If I want to bulk shop for sweaters, I go to TJ Maxx or Goodwill. Some of my all time favorite sweaters are second hand.
2b/3a.