Three questions on a paragraph

The passage below is from A History of the Index by Dennis Duncan.

It is a glorious twofold attack. Part of the great fun of King’s index is that the locations are real ones. If we follow the reference to ‘His Collection of Asinine Proverbs, p. 220’, we do indeed find ourselves at a page where Bentley is accused of citing the same proverb – about an ass– at two different points in his Dissertation. The surface-level joke of ‘A Short Account of Dr Bentley’, then, is that a time-poor reader really might need to check the details of some particular facet of Bentley’s awfulness and be delighted at the provision of a functioning index. At the same time there is a covert attack, a sneer at the ‘second-hand critic’, dependent on indexes and always at one remove from literature itself.

I have three questions in this passage.

First, the real meaning of ‘asinine’ and ‘ass’. I know ‘ass’ can mean both ‘stupidity’ and ‘an ass as an animal’, but I’m not sure which meaning is suitable in this context. I think the latter meaning is better since the reference to ‘ass’ is to criticize Dr. Bentley, the ‘second-hand critic’ as they said. (Am I right?)

Second, the meaning of ‘surface-level’. To me it means the opposite of ‘covert’ in ‘a covert attack’, so its meaning is ‘revealed or exposed’. (Am I right?)

Last, the meaning of ‘The surface-level joke of ‘A Short Account of Dr Bentley’, then, is that...’ I read this part can be paraphrased as ‘The purpose of the surface-level joke of ‘A Short Account of Dr Bentley’, then, is that...’ (Is my reading All right?)

Thanks in advance.