I have never used the DM50, but my DM100 also has these three modes, and the wide settings provides an opening angle of 120°, the center setting is still 90°. This means, if you are 20 feet away from the stage and the speaker are 40 feet (or less) apart, the center settings will do just fine and you'll collect less noise from the surroundings.
If this is a semi-professional gig by any means, try to get a mic closer to the speaker (clip on would be perfect). From 20 feet away and with speakers, you will not get good sound. Understandable, but not good.