Hi Boby!
About #4: It is just the default behavior of the engine to spread out the lines accords the platforms. But if you want to force a line to use a certain platform, I would suggest using waypoints.
About #10: I´m not sure if I understand your question. The point I was trying to make is that a Train will reserve the whole path. This will not block other trains, even if it will pass a crossing. Here is a good drawing from the OpenTTD wiki showing the difference (and advantage of path signals):
https://wiki.openttd.org/images/8/80/Difference_block_path_signals.png
Best,
Tom