Here is the full dialogue for Spawn!Astarion reaction to the player sleeping with Mizora. I used this parser to get dialogue and voice files. The dialogue does not trigger yet in game!! So this is a spoilers.
Please DO NOT REUPLOAD. Only share the link. It took me ages to put it all together, but also this is technically not in game yet.
To understand the dialogue tree, this is how it looks (I added a picture in cut):