g_a_w, MR: It is not always possible to give your wife from your own becher/challah. I was advised that if I thought my parents/in laws would perceive a slight that I should cut my wife’s piece and then cut another to give to that parent and then give my wife the first piece that I had cut for her.
oomis: there is no such things as a blanket statement, every case is different and there will always be the exceptions to the rule.
Out of curiosity. Is Shalom Bayis a din d’oraysa or is it just an emtzaus that is necesary for the mitzvos of kidushin and pru u’rivu? Before you start hocking me with “v’seemach es ishto”, the chinuch only counts that mitzvah as referring to the fact that a man shouldn’t leave his house for the first year of marriage- but he brings at the end that for a dvar mitzvah (I assume such as kibud av) it is not considered being mevatel this mitzvah and he adds that some say it is even mutar lechatchilah.