With D'artagnan and Porthos in the storage building, men approach armed with matchlocks and wheellocks. But the matches in the matchlocks are not lit, rendering them inoperable. No one would approach a fight armed with an unlit matchlock with the intention of lighting it when the fight started. That would make them vulnerable. Rather, one would lite the match first, then proceed into conflict.
Events happen in France, however text on the tomb is in English.
25 years from the death of King Louis' father is May 1635, however in previous episode Dauphin turned 6 years old (being born in September 1638).