1. I had the same responses and I think BDJ just removed that dialog when he removed the Loren Steele and Riverstride Plans quests. An oversight I'm sure.2. I had no problems with the trumpet quest. The meeseger showed up in Tularea for me in the 3rd month of the war normally.
3. I didn't kill anyone in the castle, but noticed as you say, that all archers turned red. I still got the paintings as you did and the castle was not closed to me. The same thing happned when I decided to try Fort Riverstride anyway. I went in the back door under invisibility s usual and as I was walking down the passage in there (still invisible), all the srchers turned red but the swordswomen remained green.
Your game is progressing much the same as mine ususally does and I found that I had to train after choosing the light patj. You will find that Maximus' quest is very difficult for a level 1 party, although possibly with many saves/reloads is can be done. I play "iron man" so saves/reloads are out of the question for me.