Is the mitre worn by the Patriarch the usual headgear? Is there a Antiochian mitre or crown ever used?
The Patriarch and Bishops all wear mitres. On closer examination of certain photographs, you may notice a black hood beneath the mitre. This is a symbol of the Maronite descendancy from the monk, St. Maron. The Maronites retain a far simpler form of headgear - no crowns. In public, the Patriarch wears this headgear (no idea what it is called).
I note that the Patriarch is giving out an unleavened host. I didn't know the Maronites were azimites. To the best of my knowledge all other Eastern Rite Churches in communion with Rome use leavened bread. Is there any movement away from the unleavened to the leavened bread in accordance with Eastern tradition?*
The Maronites use unleavened bread. As to any movement away from that, I am not aware. Recall that the Maronites over the centuries learned how to "take and give". In accepting certain changes from the Latins, they gained a seminary in Rome.
Do you plan to watch the replay this evening? These images do little justice to the assemblage of Eastern Rite dignitaries. They even had a Maronite choir, replete with Middle Eastern instruments.
Judging from what I saw, the choir is composed strictly of religious.