Let's look at the most common and easy fix first before looking for other causes:
(1) For the venting problem, one of the causes is a disconnected small vac hose near the power brake booster. Carefully check the area on top of the power brake booster under the hood.
(2) AC not working after few miles of driving may be caused by a slipping fan belt. The rpm sensor detects the slipping and shuts off the compressor. Check the condition of the fan belt and the belt tensioner. You may have more than one problems with the AC system, but at least, you have to make sure the belt is working properly before moving on to other areas.