I'll take a stab at a couple of your questions
1) I recently did the exact same thing with the same results. I assume that not all the old fluid is ever drained + the lining of the rubber hose parts probably contribute to this coloration effect + it seems that synthetic fluids like this often have a dilutive effect on the glaze and varnish deposits that are characteristic of past dino fluid use.
2) Don't know for sure but a good quality hydraulic hose will work for sure and probably any similarly sized reinforced neoprene hose would be serviceable or you could visit the dealer!
3)I'm not sure of your exact setup but it appears that it is the overboost limit switch you have bypassed. This is probably not good as there is effectively no limitation to the increased stress that turbo charging could subject your engine to. The theory is that more air and fuel will be combusted than your engine's cooling system is capable of handling and some engine parts will overheat and eventually fail, pistons, valves, and cylinder heads are closest to the combustion occurring. Will you operate your engine at a high enough speed and for a long enough duration to have this happen probably not but at the cost of engines and their parts would yo like to find that point of no return!
4)Not sure about the "steel clips" your referring to, on my vacuum system small steel clamps secure plastic vacuum pipes and rubber connecters together, these are loosened and tightened by Philips head screws. Banjo fitting/connectors are a fitting that is bolted through with a hollow or perforated bolt allowing some fluid/gas to pass out/into a device through the inside if the bolt and through the section of the banjo fitting that surrounds the hollow bolt stem. Usually this fitting application effectively forms a 90 degree turn in the hose or line. A common easily viewable application for these banjo fittings is the connections into and out of the canister fuel filter housing. You unbolt the through bolt and remove it thereby freeing the actual banjo fitting itself. Seals or washers either aluminum or copper are often used on both sides of the fitting to seal the connection and some through bolts may have an o-ring or two fitted on their bolt stem. The banjo fitting itself is shaped somewhat like a banjo with the bolt going through the doughnut shaped body and usually a hose bib fitting for the neck hence the name "Banjo" Some of thse answers may help!
Yeah see zbenz's post, by your updated desciption these sound like compression clips. A pair of regular slip jointed pliers with serated jaws works great. These clips are designed to be always applying presure. The only place I've run into them on my car is where the low pressure PS hose connects to the steel pipe ends on the resevior fitting and the steering box fitting.