Yes to most of those questions , and I will tell you to Read and download the TM's on your A3 that are on this site and do a search ,a lot has been written on this subject . They will explain the operation of the CTIS system and your vehicle in general . The CTIS system was a stupid system engineered by MORONS . When it works it's great , but it does require lots of maintenance to the air system/wheel O rings , quad seals , etc ,etc . The leak in your tire is probably a wheel rim/air valve o ring . The system is supposed to bring all the tires up to equal pressure , problem is that there is a LOT of places to cause problems , some simple , some NOT . The system was designed so that the tires could be aired up or down from the cab control panel . BTW , I removed my CTIS system and went to the A2 bearings and seals , MUCH BETTER , and for YOUR safety , please read the operators TM and perform your PRE TRIP inspections before your next trip . I would recommend you PM service your A3 , it will help you understand the systems and help prevent problems on the road . BTW , I have some used air valves and other parts if you need them . GOOD LUCK !! and welcome to the site , Bob k