You could ask for first delivery in the morning (which I believe would be 9:00 AM - pickup at the hotel at 8:30 AM).
Do the formalities (an hour) and out of fairness spend another hour going over the car, getting it setup, etc.
You could leave the FDC by say 11:00 AM - but why not stay until noon then and have a free lunch on Volvo?
Leaving the FDC it is a leisurely drive south to Malmo - figure roughly 3 hours / 300 km. Nice road - not much traffic.
From the bridge to Rodby ferry figure another 1.75 hours / 175 km.
Scandlines runs the ferry between Rodby and Puttgarden (Germany).
https://www.scandlines.com/tickets-und-tarife/tickets-and-prices/puttgarden-rodby.aspx
A ferry generally leaves every half-hour at 15 and 45 minutes after the hour ... so worse case you have to queue and wait a half hour. Transit time is 45 minutes. So call it 1.25 hours max to land in Germany.
That's a total of 6 hours from the FDC to Germany - and if you left the FDC at noon it would be dinner time by the time you got to Germany. Even consider grabbing a quick bite to eat on the ferry ...
Also note: 20 May 2016 is a Friday - you may run into extra traffic ...
On that date the sun sets in Hamburg around 9:20 PM - so you still have plenty of daylight left.
From the Puttgarden ferry to the outskirts of Hamburg is about 1.5 hours / 150 km.
I would expect here and possibly going through some other major cities in Germany you can expect traffic, etc.
For me I would probably not try to go beyond here in the first day.
Yes - while the autobahn can be nice and fast, also remember that in areas of higher population density there are speed limits. Traffic, congestion, accidents and construction can really affect your travel plans (add time).
If you were to stay just north of Hamburg on that first night you could head south on the A7 towards Hanover and towards Frankfurt. That would be around 500 km and maybe even under 5 hours. Given that is also Saturday morning you should be able to avoid the Hamburg weekday traffic and make good time heading south.
I'm not familiar with driving around Frankfurt and points south from there. But as you head south from your first night's stop - maybe consider not going to Frankfurt but continue east of the city on the A7 (and maybe avoid the Frankfurt traffic?) I've stayed in Wurzburg - nice area.
Personally I'd try to get as far south in Germany as you can - as the next segment to Aosta is going to take you through some pretty scenic places.
Remember to consider time for fuel stops, meals and getting the vignettes necessary for some countries:
http://www.tolls.eu/
Another good mapping tool is ViaMichelin:
http://www.viamichelin.com/
Whether using the Michelin or Google maps site I usually add some time to routes - sometimes as much as 20% - and my experience is you often can't realize the times these sites will quote you to get from point A to point B.
One last thought: Italian ZTL
Do some research on this one and since you son lives there ask him. Driving in the Zona Traffico Limitato can really incur hefty fines!!!
http://www.visitatorino.com/en/how_to_move_by_car.htm