The range at the moment is about 6 feet.

It didn't really improve even by cutting the series resistor for the LED in half.

Something must be done.

I currently have an XZTNI54W IR emitter, which has a spec of something like 2 mW/sr. My guess is that that's not enough. Switching to a VSMY1940X01 and dropping the series resistor down to 20 Ω or so should crank out more like 10 mW/sr, from what I can tell from the datasheet. Time will tell.

EDIT: Huh. Through-hole emitters can be had that will do more like 500 mW/sr. I'll have to give them a try.