Matzah and Wine on Pesach

Tamar Berger writes:
How much Matzah does one really need to have on the Seder night?
Additionally how much wine does one really need to have?
Is grape juice okay??

Rabbi Jachter writes:
The Shaarei Teshuva (O.C. 486) and Mishnah Berura (486:1) adopt a compromising view regarding this issue. They rule that for biblical level obligations we should follow the strict ruling of Rav Landau. Regarding rabbinical level obligations, we may rely on the traditionally accepted smaller Shiurim. Thus, since the first Kezayit of Matza and the Afikoman might be required biblically (see Rashbam Pesachim 119b s.v. Ein Maftirin and Rosh Pesachim 10:34), the larger Shiur of Matza should be consumed for both of these occasions. In addition, by consuming the larger shiur one thereby accommodates the preferred practice of eating two Kezeitim for both the Matza that is eaten at the beginning of the meal and the Afikoman (see Shulchan Aruch 475:1, Mishna Berura 477:1, and Rav Yehoshua Neuwirth cited in Nishmat Avraham 4:68). However, since the Matza eaten for Korech is only a rabbinical requirement, the smaller Shiur suffices. According to Rav Moshe Feinstein, (Kol Dodi 14:11 and 18:3) the Shiur of Matza for Motzi Matza and the Afikoman should be 6.25 by 7 inches and the Matza for Korech need only be 4 by 7 inches (for more sources on this issue see Nishmat Avraham 4:67-70). Since the Mitzva of the four cups is only rabbinical, the smaller Shiur suffices.
According to Rav Moshe Feinstein (Kol Dodi 2:6), 3.3 fluid ounces suffices for the four cups of wine. When the Seder falls on Shabbat eve, the larger Shiur is required since Kiddush is a biblical requirement. According to Rav Moshe Feinstein, the larger Shiur is 4.4 fluid ounces. Since some authorities believe that Kiddush for Yom Tov is always a biblical requirement (see Minchat Chinuch 31), it is best to use the larger Shiur for the first cup at the Seder even if the Seder falls on a weeknight

Regarding grapejuice, see the following link:
http://koltorah.org/ravj/15-27_May_We_Use_Grape_Juice_for_the_Arba_Kosot_3.htm