Can try and answer your questions:
1) You need an air start and a GPU. Technically the Air start can be used to power the packs but this isn't usually done as its very inefficient, in fact some of the air start units aren't designed to give high pressure air for that kind of continuous usage.
2) you need around 40 psi to start an engine. I don't know what the conditioned air pressure would be, not that high since the air is pre-condition and delivered straight into the mix manifold, it doesn't go through the packs.
3) its just normal conditioned air, so around 22degs.
4) you start no. 1 engine first as the GPU and air start are on the right hand side next to no. 2! You then disconnect the GPU and air start and push back. Once clear of anything behind you do a cross-bleed start from the started engine. You have to be a little careful with whats behind you as you have to increase thrust on no. 1 engine to around 35-40% to give the required pressure to start no. 2.
5) like I said you need around 40 psi to start an engine, the air start will not provide air for bother, when starting the engines from the APU you turn off the packs as well remember!
Hope that helps.