Wolf (and everyone else):
Before you decide whether you need to keep a minhag, first find out if your family really has the minhag or its just something “picked up along the way”, as “a nice extra”.
Personally, I do not have the minhag to make a cut in the challah. As with many things why I got married, my Rov told me there is no reason and it is detrimental to “add” for the sake of following other’s minhagim (granted, I have some strange ones, but after some research they seem to be mostly Yekke/GRA based).
Of course, if you do have the minhag, you should keep it even if you don’t understand. In your case, Wolf, if you do learn it is your family’s minhag, might I suggest making the cut and then starting to cut from wherever you want if its not seen right away?
Feivel: If you are eating a Shalem during the week, you are supposed to make a nearly full cut before the brocha & break off afterwards. I believe this is due to halachos of “Shalaym” for Lechem Mishna being different than those of Bracha, but my memory may be going on me.