#1: Yes. When you go on the Burn Retros special order you still perform a move, you may simply choose to make it a movement of 0 cm. As a result any effects which occur when you move into base contact with another game piece (ie: Blast Markers, Ordnance, Other ships, Celestial Phenomina) would still be triggered when you move 0 cm.
#2: No, it doesn't. The two rules are deliberately separate as they represent different things. Special Orders represent the "admiral" of your fleet giving complex orders to each ship or squadron and the test is to see how well they react to and implement said orders. The reason you cannot try to place additional ships on special orders after one ship has failed its command check is that the breakdown in communication has occurred between the higher chain of command and that ship, and said failure causes enough chaos and confusion that any additional orders are lost or fail to reach their targets in time for them to be relevant.
By contrast Disengaging is something that each ship does on its own independent of the higher chain of command. As a result the leadership test to disengage represents the ship itself doing what it has to to disengage, not it interacting with its external chain of command. As a result you can attempt both in a turn.
#3: Interesting question that I had never considered before. Initially I was going to say no, but your reasoning is pretty sound an it would make sense for it to work as you suggest. As such I'd lean towards saying yes. This is definitely something that needs to be clarified when this scenario is rewritten, as it is a great question. I'd recommend that it provide only a +1 bonus to the roll for a ship arriving from reserve, that way its not easily abused. Plus it would make sense that a small fighter wouldn't be able to provide as much information or guidance to a warship as another warship could.
#4: Yes they do. Again its a great question and should be clarified in the rewrite, but think of it this way: the reinforcements disengaged from the battle before actually reaching it.
#5: None of the original Scenarios for this game are balanced dude. Eldar are SUPPOSED to have the advantage you are expressing in the Escalating Engagement scenario. My recommendation is that you play it on a larger table, several of the scenarios work better when played on a larger table. Heck the Convoy Scenario works better when played on an 8'x4' table, my group realized that during our last campaign. If the table is larger it forces the Eldar player to have to move further to reach you. This game really is radically different when played on anything smaller than a 6'x4' table.
Again the scenarios need a rewrite, and that has been underway for a long while but I haven't been afforded the opportunity to see the in process rules as they are now. One thing that could work for Tau in that sort of scenario would be for us to amend the Tau fleet rules so that Gravity Hooks would cause ships arriving from reserve to also show up with their escorts in tow, so you would have groups showing up in tandem. Just tossing out an idea.
Overall great questions, I hope I helped.
