1)
Why didn't Pharaoh say to Moshe outright, "Go and sacrifice in the desert!"
1.
Oznayim la'Torah: Because, still afraid to lose his precious slaves, Pharaoh had in mind to retract once again. Meanwhile, however, he needed to get rid of the wild beasts, so first things first, he begged Moshe to pray for him.
2)
Why did Pharaoh ask Moshe to pray only for him?
1.
Oznayim la'Torah: In his conceit, he forgot to include his servants and people - but Moshe (in the following Pasuk, 8:25) did not.
