'Yonder' is both adjective and adverb. Here an adjective in the sense of pointing at something or someone at distance within sight. It differs from 'that' ,because it could refer to single and plural entities. It serves like both 'that' and 'those',you could also say: "which doth enrich the hand of yonder men" ( where men is a plural noun). Note that the usage is archaic and Skakespearian ,so no wonder Bradley never heard it this way. The way it is used till now is rather as an adverb !

I've never seen it used like that. I've only seen "over yonder" or "out yonder". In those case in means there. We use it where I live to sound more hick like. Shakespeare is difficult dor English speakers sometimes because he uses words in weird ways. That is because he wrote so long ago.