just as an aside, I drove a re-mapped hybrid turbo'd 05 plate today courtesy of littleGTV, a fellow forum member, and at 189k on the clock it pulled like a train!!! so your high mileage is nothing to worry about, the CF3 engine had no swirl flaps either so you have a potentially solid car on your hands when you get the issues sorted.
turbo in that late will either be MAF or MAP sensor or collapsed or leaky vac hoses, or boost leak, the VNT may be sticking as well, the good news is the is is all fixable...it shoulb be in before 2k so its very late boost.
I would highly recommend you get an elm327 and torque app pro on your phone, this will allow you to read codes and may point in the direction sufficiently to tackle some of the easier things yourself.
airbag is most likely a failed/failing connection somewhere or maybe even just a random code generated by an electrical gremlin..you willl need the code cleared at a dealer unless you have a full copy of Multiecuscan or similar...had a similar problem this week with my other Alfa (GTV 2.0 TS) and once the code was cleared it stayed cleared.
the exhaust blow at the front is likely to be the flexi pipe (known common failure point) and replacements are available on ebay for cheap..around http://www.ebay.co.uk/itm/Alfa-Romeo...3AAlfa+Romeo|M
+1 for Autolusso Penrith ..Dan will get it sorted for you...