1) APU exhaust. Gripen has it more towards the back, also gets dirty. Rafale just behind the tail fin root, not so dirty. And F-22 also port side, about same position as the Typhoon, only because of the high wing, it doesn't hit the aircraft so much. F-35s (or at least the prototypes) have it on the starboard side nacelle, between the intake and the wing, which also makes the entire starboard dirty.
2) I guess the Paveway's would impose a G limit lower than the aircraft's?. I don't know about airshow performances, but results from the IOC test flight of the Block 5, were very positive with regard to handling the heavy loads. And they went to Nevada this year for a CAS exercise and flew with 6x 1,000lb Paveway II, Litening III pod, and ACMI pod. Not live firing, but to pass "multi-role operational employment declaration". So why would they stick 6 dummies under it then, if the aircraft would not handle it? Even with real AAMs, it's still not the heaviest load we've seen on jets. I'm wondering about tanks + bombs, would that mean max 4 bombs with 2 tanks?
I guess it is a heat exchanger or something like that.
Heat exchangers don't shoot out smoke, they only change colour themselves. Only on the Tornado the heat exchanger gets very dirty, but that's because of the thrust reversers, which paint the whole tail black