What did Yakov mean when he pointed out that the ewes and goats in Lavan's flocks did not lose their babies?
Seforno and Rashbam: He meant that, bearing in mind, his (Yakov's) total dedication when tending to his sheep, Lavan's suspicion that he had stolen from him was completely unfounded, considering the lengths to which he went to make sure that none of his ewes or goats miscarry.
Ohr ha'Chayim: Shepherds sometimes eat animals and claim that the mothers miscarried, so the owner will not know. Hashem caused that there were no miscarriages, to remove any possible suspicion of Yakov!
Why did Yakov add that he did not eat his Eilim (rams)?
Rashbam: He meant that he did follow the custom of the shepherds of that time, who would slaughter and eat male sheep. Malbim
Moshav Zekenim: Even though a Drashah includes a Palgas (a sheep in its 13th month, for less than 13 months is not called Ayil), that is for Kodshim. Here we discuss Chulin.
Why did he mention specificaly "Eilim"? Does this mean that he ate Lavan's Kevasim?
Moshav Zekenim (from Bava Kama 65b): From here we see that even a newborn lamb is called "Ayil". 1
Even though a Drashah includes a Palgas (a sheep in its 13th month, for less than 13 months is not called Ayil), that is for Kodshim. Here we are discussing Chulin.
Why did Yakov emphasize that he was with him for 20 years?
Rashi (37:34): I will be punished for this time. Yakov mourned over Yosef the same amount of years that he was away from his parents and neglected Kivud Av v'Em. 1
Ohr ha'Chayim: A thief or swindler can refrain from evil for a short time, but not for a long time. I worked for you for 20 years
Surely Yakov did not know what his punishment would be. Perhaps he said this with Ru'ach ha'Kodesh, unaware of the Drashah that he will be punished for these years. (PF)