Keep in the mind the distance involved here. To put it in historical terms, Gdansk, ie Danzig, at the mouth of the Vistula, was the capital of West Prussia, whereas where you want to go, the Wolf's Lair, near Rastenburg, now Ketrzyn, is in East Prussia.
I would go from Torun to Olsztyn, the terminus to transfer to Ketrzyn (Rastenburg). Better that you stay in Ketrzyn.
In 2005 en route to Torun from Poznan where we had transferred from Berlin, (we spent the night there after all day from Paris), the Mrs and her mother got into a conversation with a couple of Polish students talking in French since we were all sitting together. I never asked them if they spoke English, they knew we were from here, and everyone was fine speaking in French, except me. We told them we were heading to Torun.
One of the girls told us that they were going all the way to the terminus, Olsztyn, which meant nothing to me until she mentioned its former German name, thinking that might ring a bell, Allenstein. It most certainly did since I knew Allenstein was in the former East Prussia and the 1914 Russian invasion objective.
Even from Olsztyn it's still a distance to Ketrzyn (Rastenburg) but it's direct.