I, too, have labored over the counting of the days. I like you I have come to the same conclusions. Jesus said that he would be, like Jonah, 3-days and 3-nights in the heart of the earth. (Matthew 12:40). That is 3x24 hour periods, not parts of days. If Jesus died at evening on Friday, then 3-days and 3-nights takes us to Monday 6pm, not Sunday morning before dawn.
Jesus was crucified on the day of preparation, the day before the passover which starts at evening (see Leviticus 23). This is when the passover lamb is to be sacrificed. Jesus is the passover lamb (1 Corinthinans 5:7). So, here is the time line using our mondern am/pm reckoning, but overlaying it on the Bible's evening/morning reckoning:
The Sabbath that was approaching was NOT the weekly Sabbath but the starting of the Passover ("for that sabbath day was a high day" John 19:31). This unchains us from the weekly Sabbath fixation and we can work backwards from the discovery of the empty tomb. Since Jesus was already risen Sunday at dawn and he said he'd be three days and three nights in the heart of the earth. That takes us to Wednesday at evening for the placement of the sacrifice of the passover and his death on the cross. Projecting forward 3x24 hours takes us to the end of the weekly Sabbath.
Thanks, that was very helpful information.