Characters repeatedly mispronounce "Hereford" as "Hair-ford". The character is called "HERFORD" in the text. That is how Shakespeare wrote it and intended it to be said - the production is respecting that. Pronouncing it "Hereford" doesn't fit the poetic metre. Spellings and pronunciations were simply far more variable then.
A character uses a telescope. Richard II died in 1400. The telescope was not invented until 200 years later.