Q: Is it possible that we do not have Shalom Bayit and do not have children because we have an invalid Ketubah?
A: There is no ancient source for this. It is necessary, however to have a Kosher Ketubah according to the Halachah (see Shut Mishneh Halachot 14:86).
Q: Do interlaced hands impede the abundance of luck descending onto a person?
A: Nonsense. There are some who refrain from interlacing fingers based on Kabbalah. Zohar, Vayikra 24:1. But this is not found in the Halachah. According to the Halahchah, one should refrain from interlacing their fingers during the Shemoneh Esrei. Taz, Orach Chaim 95:1. Aruch Ha-Shulchan ibid. #7 (and see Ta'amei Ha-Minhagim, Likutim #24. Ben Ish Chai, Pinchas #18. Kaf Ha-Chaim, Orach Chaim 91:28. Shemirat Ha-Guf Ve-H-Nefesh 78:1. Piskei Teshuvot 95:5. And see Ha-Rav Yosef Shalom Elyashiv who interlaced his fingers when meeting with the Tzanz-Klausenberger Rebbe: http://www.youtube.com/watch?v=5dKkwC2YiOw).
Q: What is the source that it is a Segulah for finding a match if one eats from the Challah on which a groom recites the blessing?
A: There is no source.
Segulah for a Happy Marriage
Q: Baruch Hashem, I am getting married. Is there a Segulah for a happy marriage?
A: To repent and learn Mesilat Yesharim (And so too Ha-Rav Ben Tzion Mutzafi in Shut Doresh Tzion: To completely repent and establish fixed times for Torah learning after the wedding).