The adverbial use of the definite noun the most synonymous with the bare-adverbial most to modify an entire clause or predicate has been in use since at least the s and is an integral part of English.
Most is what is called a determiner. A determiner is "a word, such as a number, article, personal pronoun, that determines (limits) the meaning of a noun phrase." Some determiners can only be used with either a countable noun or an uncountable noun, while others, like most, can be used with both countable and uncountable nouns. Uncountable nouns usually take a singular verb. So, in your.
Since "most of _____" is a prepositional phrase, the correct usage would be "most of whom." The phrase "most of who" should probably never be used. Another way to think about the difference between the subjective/objective pronouns is to revise the sentence to include a personal pronoun and see which form (he/him or she/her or they/them) fit.
I've recently come across a novel called A most wanted man, after which being curious I found a TV episode called A most unusual camera. Could someone shed some light on how to use "a most" and wh.