Hey Gem,
Well, that does sound like the air pack. I'm not an expert on it, so anyone with a better idea, please feel free to chime in. Here's my thoughts.
When I got my A3, I sprayed a little rubbing alcohol mixed with marvel mystery oil into the feed on the air compressor. I did the same thing on my 109a3 as well, and it seemed to help a couple of sticky valves. If that's all there is to yours, which it might be given the fact it was working ok at first, that might help. I opened the bleed valves on the tanks, and sprayed the mix until it came out the bleed valves. You may have to push the brake pedal a few times while you are adding it.
Double check your tire pressure. I have heard strange stuff about a tire with too much pressure messing with the brakes, since it can feed back into the system from the CTIS.
Now to the other stuff. If it's only the front brakes, it's probably the right hand hydraulic unit, it controls the front brakes.
About the only thing you can do for it is to replace it or rebuild it. Bypassing it is probably suicidal.
One other thing to check. Look under the truck and you should see three lines coming from the brake assembly that go to the back of the cab of the truck, making a uturn and pointing down. These are your brake vent lines. It's possible though unlikely these could be plugged, and preventing your air pressure from venting. Easy check is to trace it back to the right hand brake assembly, and disconnect it. See if your brakes return to operation. it's a long shot.
That's all I got for you. I'd recommend a brake shop if you aren't completely comfortable with doing all this, as this is one of those things that you want to work more than any other thing. Hope it helps.
