Hej Christofe,
I have been there a few times and always took the bridges, have to admit that driving the bugs on Twingo numberplates had me want to keep moving straight home
But the Helsingborg ferry, is just a drive on/off ferry, not too expensive (you have to pay the bridges as well, was around 80 euro one way I think, so) don't think you have to wait long either and that might cut your trip to Goteborg considerably.
If you run out of gas don't take risks and fill up in time, there's a few long stretches without gas stations on the highway. And make sure the lights work, it is DARK out there at night.
There is a pizza place near Malmö where you don't want to eat, they serve the meals on carboard plates with throw away cuttlery and in hindsight it is just as well. The plate stuck to the table because of the filth on there.
And most of all have fun