The best way to adjust to the sound delay on some organs is this: do not listen to the sound in the room. I had experiences with sound delay on pneumatic organs here in Lithuania.
The first one I tried was a 19th century 3 manual organ. The first time I played it was at a concert during my student years. It was very strange for me to play Franck's 3rd chorale and hear the constant delay of sound. I knew ahead of time that this would happen. Actually, I was warned by my professor and other colleagues but to experience it personally was a very different thing.
It seems like you can't control the sound, like you can't control the instrument and it gets slower and slower every time. It's sort of similar to the feeling when playing with the orchestra - if you enter on time - you are actually a little late. It reminds me also of the experience I have sometimes in a large church when I have to play the organ and accompany the choir which is singing from the front of the church. Because of the great distance we (the organist and the choir and in some cases, the conductor as well) might be constantly fighting each other and slowing each other down.
The only cure to this problem is this: we all must look at the conductor and not listen to the sound. I mean, the choir (or several choirs placed on different balconies) and the organist must follow the movements of the conductor. That means the organist must press keys a little earlier than normal.
Actually, this is one of the major reasons we hear some church congregation members and some organists dragging the tempo when singing hymns. This is so natural - people listen to the organ and sing only when they hear the sound. The organist also listens to the congregation and plays on time but in reality - he or she is late. The cure for it is this: keep the constant pulse, ignore the singing, and play ahead of time.
So going back to this topic, I suggest you just press mechanically the keys without actually expecting to hear the sound. In other words, you must constantly be in a leading position and not following, if this makes any sense.
Yes, it sounds counter-intuitive but listening to the sound in the room slows you down. What happens is that you press the key and wait for the sound. The sound is delayed by a second, and you feel like you can't press the next note UNLESS you hear the first one. So it is a circle which slows down performance tempo.
I'm certain that after you played there for a while, you would start to adjust to the room and the instrument which also means that the next time you come back there (and I hope the pastor will grant you this opportunity) it will be easier and easier for you to play on time.
I can only tell you that this is NOT the most difficult situation. Some organs have tracker organs with pedal electric action. That means the pedals are constantly dragging. The organist must again play only the pedal part a bit earlier. THIS is really complicated.
One last tip: you must try to relax your body while adjusting to the sound delay. You see, your immediate physical response to this situation is most likely a tension. If you can't control the sound very well, you subconsciously tend to tense your shoulders, hands, and even your feet. The end result is obviously not so great - your are fighting the instrument and not adjusting.
However, while playing such organs, you should try the exact opposite - relax your body by breathing deeply and slowly through your nose. Do not depress the keys with the force - play mezzo piano. This way you will be in harmony and unity with the instrument and can control the sound delay much easier.
Use these tips when adjusting to the sound delay the next time you play such an organ. With proper preparation and practice, such performance can be quite successful and actually pleasant experience.
By the way, do you want to learn my special powerful techniques which help me to master any piece of organ music up to 10 times faster? If so, download my video Organ Practice Guide.
Or if you want to learn to improvise in the style of Bach? If so, I suggest you check out my 9 day mini course in Keyboard Prelude Improvisation.