Last time I checked the Eucharistic fast is one hour before reception. That’s one hour before reception, not one hour before mass begins. So he was probably not breaking the fast.
Yes, and some of use still observe the fast from midnight, believe it or not.
As for your brother: you were in a fix, certainly. It is a mortal sin to neglect the Sunday Obligation, so you did your best to help guide him there, but it certainly does not appear that his heart was there. Like the other poster said, you cannot commit a mortal sin for another. If I were in your shoes, I would speak to my priest in the confessional this week, as he could likely give you better discernment of this situation than any of us poster.
It certainly seems like you care about your brother, so you’ve probably already told him of the gravity of his sins, the consequences he is facing, and how he offends God. Unfortunately, many of us have family members just like your brother, and so we know how you feel. Keep chiseling away, solider, but do not let seeking after him allow you to wander away from your Shepard. You yourself have to stay close to your Shepard and call your brother from His side, so that when/if your brother looks back, he sees our Lord, and not you. It is only our Lord that brings His sheep back, none of us, but we certainly have the responsibility to call for them! If you have a chance to go to adorations of the Blessed Sacrament, perhaps you can apologize to our Lord for the sacrileges against the Blessed Sacrament that occur all over the world, including what your brother did (and I mean apologizing for the purposes of pleasing our Lord and recognizing the pain caused to Him,
not for the purposes of absolving your brother’s sins, of course, as I’m sure you know that you cannot do that). Stay strong, and keep praying for your brother!