Friend of mine is a patent attorney and fwiw this is what he had to write about using multiple references in a patent rexamination request.

"There is no rule prohibiting someone from combining multiple refences, even 5 or more, to make an argument against patentabilty. However, the arguments usually become more precarious (far less persuasive) when that many refences are combined. You could counter-argue that the combination is not something that would make sense (such as combing references from different fields)."

I also asked him about individual claims in a patent and this is what he wrote back

"All claims in a patent are separate rights (of varying scope) that stand alone. One or more can be invalidated while others can remain. A patent only needs to have one valid claim to exist.
"