1)
Who says "Hasirosi mi'Sevel Shichmo"?
1.
Radak: Hashem says so. He removed burdens from Yisrael's shoulder (they used to carry bricks on the shoulder); they were not enslaved after this. Therefore He made the Chok of Teki'as Shofar for a remembrance of the end of slavery on this day.
2)
What is "mi'Dud"?
1.
Rashi: It is from servitude of cooking pots, like other slaves. Dud is a pot - "v'Hikah va'Kiyor Oh va'Dud" (Shmuel I, 2:14).
2.
Radak: They no longer needed to make pots. They used to do all work with clay - "b'Chomer uvi'Lvenim uv'Chol Avodah ba'Sadeh" (Shemos 1:14).
