Dear @jrswab,
You are correct in that the Scriptures need to be interpreted in the light of the Hebrew culture and the ordinances of the Torah.
In regards to “Palm Sunday”:
Jesus’ triumphal entry into Jerusalem was on Nisan 10 when the lambs were selected for the Passover sacrifice, it is relatively simple to prove it wasn’t on a Sunday.
Nisan 7 is the seventh day of the week - the Sabbath (Saturday). Three days later is Nisan 10 – Tuesday.
In regards to “Three days and Nights” please read my post:
HOW WAS JESUS ABLE TO CELEBRATE PASSOVER AND YET BE CRUCIFIED ON PASSOVER? How Can Friday Afternoon to Sunday Morning Be Three Days and Nights?
Blessings and Shalom, Steven Sherman @lastdays