My two girls are 26 months apart. It will take time for Jacob to adjust, but he will. My daughters play together all the time and hug each other. My oldest just turned 4 and the other one will turn 2 in May. I am very happy to have had the youngest when I did. Maybe when the baby starts responding to Jacob he will feel differently. I think you had some terrific suggestions from other people and hang in there!
One thing I read in Parenting or somewhere was talking aloud when it's someone's turn. For example, "Baby, it's Jacob's turn now." And vise versa.