Which is the best option for improving the Pope's opinion of my character?
1) Sending my chancellor to Rome to improve diplomatic relations
2) Sending my chaplain to Rome to improve religious relations
I always have my chaplain in Rome as Catholic unless there is a province I personally hold that needs converting. Even if I reach 100 opinion I keep going, never know when you need a claim or invasion from him.
Can usually find better use for my chancellor(claim or maintain vassal's opinions).
You can lose the stressed trait through various events. I can't remember the exact criteria tbh but I think having a content character at your court might be one of the triggers.
To build on this you can loose it like you say in various events.
All the lover-events AFAIK has the chance of removing stressed(arrange a ball, show her the castle etc.)
Going on Hajj(Stoning the devil) or Pilgrimage(as homosexual)
Any courtier that has content. MTTH is reduced if the courtier is patient(4) and diligent(3), while slothful(0.2) and lustful(0.5) increase MTTH.
ROI added some events I am not familiar with, that also has the potential to remove it. There is also a bunch of events in
various_traits_events that has the potential, but I don't think these are used. I have at least never seem them trigger.