1)
Why was Amasa late?
1.
Rashi citing Sanhedrin 49a: He found Rabanan beginning to learn [so he did not interrupt them].
2)
Why is it written va'Yicher, and we pronounce it va'Yocher?
1.
Radak: It is written like a verb whose initial root letter is Yud, like Yitav (when it gets the prefix Vov to switch future to past) becomes v'Yitav (Shoftim 19:6). It is pronounced like a verb whose initial root letter is Aleph, like "va'Yosef Od David" (6:1. There, Radak explained va'Yosef to be from the root Hosif, or from the root Asaf with an Aleph.)
