Inkscape won't open the svgs in your latest zip for me. It would be easiest if you export the part directly from frittzing (assuming you are now getting a part in Fritzing of course). To do that right click on your part in the mine parts bin and select export part. That will create a fzpz file with the fpz file and all of the svg files for the part. You can then upload that file here via the 7th from the left icon in the tool bar at the top of the reply box here in the forum. The gold circles are because the relay I referenced is through hole rather than surface mount so you probably want to keep your original pcb svg and just add the connectors from a surface mount part (this is what I meant about the parts not being quite the same). As to the psu, yes you can make only one part but you are going to need to use cut and paste in (in my case Inkscape, I assume the other packages have a similar feature) to copy parts of the screw terminals in to the svg. You will need to edit the xml and probably the fpz file as well to make the connections work. If you can get to the point where you can upload a fzpz file one of us will probably be able to help you do that as it isn't simple (not much about parts creation is simple unfortunatly, that's the price we pay for Fritzings unique features).
Peter