OK, Jimmy, ready?
Cycling in Scandinavia is, IMO, a dream, especially cycle touring. The roads are mostly excellently surfaced, with relatively little traffic (away from the larger cities) with fantastic scenery. And drivers are very courteous.
The weather can be uncertain, but if equipped with the right gear, it's not a problem. In the summer months, the days are light until very late, and then only a bit murky for an hour or so around midnight, so if you're not tired, you can ride on through the night in good 'daylight' and sleep later on in the day/afternoon.
Camping, both wild and organised isn't a problem. Nor should you have any trouble with food, as long as you stock up for the day at a shop or petrol station whilst you have the chance. Knocking on a door to get water or asking for directions isn't a problem and you may even be offered a bed, or at least a tent space in the garden.
Almost everyone speaks good English, so communication is easy. As someone previously mentioned, some of the tunnels are out of bounds for cyclists, so make sure you know of their whereabouts when planning you route.
Pack sensibly and you'll be fine. Either do it yourself, or get your lbs to tighten the spokes on your back wheel, just for peace of mind, and take some spares, just in case.
With regard to your route, I'd suggest flying with Norwegian to Stockholm from Paris, take the ferry across to Turku (in Finland) and cycle the coastal road ALL the way north to the Swedish border, come down the east coast of Sweden to Sundsvall, then traverse west to Trondheim and come down the west coast as best as possible, bearing in mind there are a lot of fjords reaching a long way inland for you to negotiate.
From there you'll be able to 'do' the Trollstigen and head west towards Molde for the Atlantic Way, or the other way around, if you prefer.
Down to Bergen, Rallarvegen and pop in to stay with us for a day or two, then off to Kristiansand, ferry to Hirsthals in Denmark and slowly make your way back to France. Should be a great 2-3 months!
If you have any specific questions with regard to rules and regulations, internet weather sites, campsites, B&Bs or Youth Hostels, lbs etc, just pm me.