Have you thought of a mountain bike? My Trek 820 actually weighs less and is easier to handle then my Trek commuter bike. I paid less than $250 for it and it's the bottom of the Trek MTB choices so you could go up a bike or to and still be within your budget. It would be able to handle road riding And the fire roads you ride, plus you can put racks on it for carrying loads. It also has a lower gear ratio so for commuting it's great for any hill climbing you might need to do. It doesn't have to be a Trek, that just happens to be what I have in my "stable". You could also put different tires on it to make the road riding smoother, but the tires on mine aren't uncomfortable. It's the bike I use to commute when the Peugeot is down. I'll also probably switch to the MTB for my winter commute and do who knows what with the commuter bike (too heavy and too clunky).
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"