You're not going to cover someone with a 30' walk from far to near with anything close to an even source with a single battery-powered LED, but you probably shouldn't anyway because on a street at night, people move naturally from being lit by one source to another -- an even key light over a 30' distance is fairly uncommon unless there is a huge source of light in the location.
Certainly it's possible to cover a 30' walk evenly, there are a number of ways but most require starting out with a bigger light from farther away to reduce the rate of fall-off, and then if necessary you can use net flags and and a half-scrim in the light to bring down the intensity gradually as the actor gets closer to the source.
Instead of an even key, you could, for example, have him start out in one key light from an LED, walk out from that and into a second key as he stands in front of the theater. A third light could provide a backlight / edge (or a dimmer side light so that he never goes dark) mainly for the middle of the walk when he passes between the two sources.
Or of there is enough natural light on the street, you can just have him walk from a general underexposed available light and into your key as if the theater is lighting him.