Any sport is a set of rules and you have to comply with them otherwise what's the point in doing that sport. I don't like the rolling maul in rugby, which I consider to be legalised obstruction, but until the rule changes it just has to be accepted as a condition of playing. Similarly with headphones, if it's a rule in a race you just have to accept it. Disqualification is just a consequence of ignoring the rules wether you like it (the rule) or not..
I would certainly avoid taking the event buses. They are overpriced and there is a long walk from the finish to the bus pick up point, which is often chaotic. Best to stick to using the local bus service. The Nos 26 and 44 are the services you need. They can both be taken from the start at London Road to the finish at Musselburgh. A day pass is £4. An alternative return from Musselburgh is to hop on the cheeky First Bus Service buses that wait outside the finish park exit (not official and not advertised). They wait outside the park, across the road and to the left and it's only £1 to return to the start in London Road.
I always concentrate on my breathing during a run as it helps me get into a rhythm and focused on being in the moment. If you are having problems then you might like try these tips.
Firstly, try out different combinations of breaths in and out. I find in for 2 and out for 2 works for me. You might try 3/3, 2/3, 3/2, 4/4 etc. Experimenting with different combinations to see which works best.
Secondly, being tense in the shoulders can prevent you from breathing in properly. Relaxing the shoulders by pushing them down (rather than being up around your ears) allows for taking a deeper breath.