"He is now as valiant as Hercules
that only tells a lie, and swears it...."
See in text (Act IV - Scene I)
That is, a man now can be as brave as Hercules by bragging about his great deeds and then swearing an oath.
"You break jests as braggards
do their blades..."
See in text (Act V - Scene I)
Benedick's simile implies that Claudio is a coward—when braggards (braggarts) break their sword blades, they do so in order to avoid actual combat or dueling.
"And yours as blunt as the fencer's foils..."
See in text (Act V - Scene II)
When fencers practice, they use a foil with a blunt tip so as not to injure their opponents, so Margaret is telling Benedick that his wit is dull.