BMX gearing - for road / commuting
what spacing is the is the rear hub? I bought an s2c recently to commute on my track bike, two speed internal geared hub with a gain of 38% but it might be over kill for yourself.

Given your setup you have a gearing of about 55inches, if you were to switch out the rear cog to a 12 tooth you would gain 5inches, bring you to around 60 which is considered a fairly spinny ratio on a track bike.

Easiest way is to switch is the back free wheel. However it seems the lowest freewheel available is 13 tooth so you are limited. You could get a new chainring up front which would achieve the same but may need to buy a new chain too.