Q. If one is in doubt if he made Kiddush Friday night, or if it was made correctly, he cannot repeat it (although it is good to hear it from someone else).
In the event that he cannot hear from someone else, he is allowed to eat normally, although it is forbidden to eat before Kiddush.
Would it be an act of piety to eat the bare minimum that one is required to eat on Shabbos, in such a case, as every bit of food that one enters into his mouth is possibly a transgression of eating before Kiddush? (Obviously, this is talking about a person who is on a high madreiga…)

A. Mishna Berura (289: 10) rules that if someone does not have any wine, chamar medina or bread on Friday night, if he thinks it is likely that he may get some later, he should wait a couple of hours, but not after chatzos. If he is hungry or weak, he may rely on the kiddush (vayichulu) said in maariv, eat what he has, and not nullify the mitzva of oneg Shabbos. When the wine or bread arrive, he recites kiddush and eats a kezais of bread. The above applies if he had in mind to comply with the Biblical mitzva of kiddush when he said vayichulu, otherwise he should repeat it. (Mishna Berura 271: 1, Shaarei Tzion ibid 4).
Horav Shlomo Miller’s Shlit’a opinion is that when in doubt if the kiddush was said correctly or maybe even not at all, he should make only the brocho on the wine, since reciting a brocho when in doubt is a Biblical prohibition, while eating without kiddush is only Rabbinical, and permitted when in doubt. (See also Piskei Teshuvos 271: 7)

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a