this pattern is written for 15-17” waldorf inspired dolls, but you can adapt it for 18” dolls by using sport weight yarn and bigger needles (4 or 5 i.e).
the cardigan is not supposed to have ease, it’s designed to be worn on a puffy dress, that’s why it’s short… the wide sleeves are supposed to be turned back, but your doll will choose by herself her favorite way…

the sweater is work in one piece bottom up from the back.