Should women say the beracha of Hamapil before going to sleep?
Also, it seems that most people do not say the entire nusach in the siddur for krias shema she’al hamita and just say krias shema and hamapil. Is there any limud zchus for such people?
Magen Avraham explains that the reason for which women generally do not say the blessing of Hamapil is because the blessing is only recited at night, making it “time dependent” and exempting women. However, acharonim have written that today women do recite it, and dispute the reasoning given by Magen Avraham. If I remember correctly, according to dictates of kabbalah women should not say the berachah, though I have not presently found the source. Kaf Hachaim, however, writes explicitly that women should say Hamapil, and adds that they should also say the additional mizmorim (239:3).
Concerning the passages of keiras shema al hamitah in the siddur, those verses and passages that have a source in Chazal take precedence over extra pesukim that appear (see Rema, Orach Chaim 239:1). When asked whether one must say the entire nusach or not (the question was asked by someone who regularly fell asleep before he finished it), Rav Elyashiv shlita responded that “all good yiden say it!”
Sources: Magen Avraham, 239:2; Pri Megadim, Eishel Avraham 239:2; Shaar Hatzion 239:15.