The first blank seemed easy. So, attack it first: the film critic realized he had been presumptuous in his judgment of her ability -> means whatever he thought about her skills earlier was wrong and this is further supported by he berated himself for not realizing it sooner. After that, presumptuous in his judgment of her ability focuses on the fact that she wasn't good like the critic earlier thought. So, her performance must not be exhilarating or scintillating then it must be bland or vapid. Then, if you look at the options it can't be A, it will be the opposite of bland, then C can be construed as 'Okayish'. So, by eliminating A and C, you can choose B (I had no idea what grating meant).

On screen, her impassive delivery combined with her -> It is important to understand this part as it supports the upcoming 2nd blank. When you are impassive you are not actively participating and her ___ blank mannerism complimented her impassivity. So, if you can't find any word to fit in 2nd blank you can put impassive too as it implies the same idea, and bland, vapid also works. Now, her mannerisms reminded him of a mannequin, a mannequin is a dummy with no life but the author goes on to say with just enough life to pass as a human implying it had just enough life to be considered as human. So, the 3rd blank can be thought of as it had little life. Now, look at options our guess for 2nd blank was vapid, bland, or impassive out D, E, and F, only E is near to our guess which is her performance was wooden not very lively. As for the 3rd blank, G is closest to our guess as it had just enough life to be considered as human.

B, E, G