1)
Will only the sailors be in the ashes?
1.
Malbim: No ? it says above (16:16) "v'Yardu me'Al Kis'osam Kol Nesi'ei ha'Yam."
2)
What is the meaning of "Yispalashu"?
1.
Rashi: They will roll. Radak ? this is like "v'Hispaleshi va'Efer" (Yirmeyah 6:26) - rolling in the ashes to cover oneself.
