Hello I really need your help, :) 

I want to travel from Stockholm to Gällivare in August with nighttrain and interrail. I did this last year, but this year the booking system is very strange. On sj.se the trains are not avaible yet. On sj.se even the trains for for June are not avaible yet. When will they put the trains on their website?  On vy.se they are avaible. But is it possible to buy the seat reservation for interrail on vy.se? When I want to buy a seat and I type my Interrail Pass Number as discount it wont get cheaper than normal price. If it is not possible to only buy the reservation for seat for interrail - is it possible on other websites?
On vy.se I saw that the train connection is 14hours in July and 17hours in August, why? Will there be a 14hours one in August released soon?

Thank you very much for your help
Paul