Hi Martin,
1a
if you hit your space bar your ‘user coordinates’ are set to 0|0-
so you can make delta meassurements this way.
1b
in the context menu there is an entry ‘Export Pad Settings’
and an entry ‘New Pad Settings’
the second transfers the ‘exported’ settings to the new pad.
–> other way is to save your work - close the editor and open the *.kicad_mod file in an text-editor
there you can use search&replace 
2
what do you mean with devices? footprints?
in PCBnew
you can draw select multiple footprints with an ‘border selection’ - just click and drag.
after you have released your mouse button there is a dialog with different options:
there you can choose what should move…
-
relative - you can use the ‘Highlight net’ button (second from top in right side vertical toolbar)
if you click on a pin / pad your Eeschema should jump to this position on the schematic -but i don’t know of a highlight option in Eeschema. -
i don’t think so - in Pcbnew it defaults to grab all things that are ‘touched’ by the selection
-
look at the Menu ‘Design Rules - Design Rules’ - there opens up an editor there you can define some ‘Net Classes’ - i normally have one for power -
in the second part of this dialog you can choose what Nets from your project should belong to which Net Classes:
the units in this dialog switched if you switch the units in the main Pcbnew window.
additional you can switch what custom size is active in the
these sizes are defined in the Design Rules Editor in the second Tab 'Global Design Rules:
6
the tracks will be deleted. but you have to manualy export the netlist in Eeschema and import it in Pcbnew.
at the import there is an option ‘Unconnected Tracks’ ‘Keep’ or ‘Delete’.
i highly recommend to read some of the tutorials and - also the getting starte documentations / reference manuals for the tools (available in the help menu).
there are really useful tips and tricks in these documents…
sunny greetings
stefan