....uh, I was thinking the booster itself; if it's damaged internally (the diaphragm) it can leak internally. Replace the hose all you want -- if the leak's internal to the booster, a new hose - even a zippy tied one - won't help any.
The light dimming is because you're hitting the brakes making the brake lights come on. It may be that your alternator is on it's way out. Do you have under drive pullies? How many volts are at the battery when the car is idling?
~12.6 volts and above is where you want to be. Less than that and you are discharging the system. However, it can be normal to see a state of discharge at hot (stock) idle with some (or one ) accessory turned on. U/D's can make it worse.
The light dimming is because you're hitting the brakes making the brake lights come on. It may be that your alternator is on it's way out. Do you have under drive pullies? How many volts are at the battery when the car is idling?