Well, to begin the tower is not original but was an effort at modernization of the kind thought necessary around 1867. The building is ancient though and dates to the 12 century with some unique masonry workmanship. Anyway to the point. That door was always one of the more interesting features for me too. In fact I had intended to look into giving it some needed attention but never got further than repairing the arched trim which had fallen down. The hinges are authentic and likely even older than the door itself and differ from hinges used in houses or farm buildings, maybe because this is a church. They are attached pretty precariously only to the trim. I believe it is what you called a board and batten door, with three battens on the opposite side. But the construction is consistent with similar doors I know of, that is tung and grooved planks nailed from the batten side through and clinched.
Of the five ladders I had to climb to get in the top of the tower this and the one under it were fairly old and similarly built and I know at least the one under here was, like you describe, from a single, split through pole. The rungs always are flat, through morticed, shaped on the under side and pegged at every rung or every other rung. Mostly they are made from North American softwood like Douglas Fir because of advantageous strength to weight ratios over long lengths.
I can't tell what is written in the bell because other than the Latin there, the rest of it is in Friesian and my Friesian is very poor. An interesting thing is though that the Nazis stole the bell from the tower during World War 2 and took it back to Germany intent on melting the brass down for bullet casings or something. Thanks to their obsession with documenting the whole plunder though the village folk were able to track down and retrieve it. Of all the clock towers around here this one does have a uniquely long and clear resonance. It is located in the village of Ee.