Do have a look at the second oldest town in Denmark.
There is an Aire very close to the centre. ( big no camping signes) but fine to stay.
Strangely the last 200M has a 3 ton limit but the lorry car park is opposite the Aire!
Denmark can be cold wet and windy in April, Sweden is beautiful in May with all the spring time flush of new growth.
You may find garages in Sweden selling CNG , compressed natural gas. IT IS NOT THE SAME AS LPG. LPG is available at some places.