Hello and thank you for the feedback. I'm glad to hear you enjoyed the route even without much liking Bastien.
Hmm, the only circumstances where Bastien should ask for a divorce are if in the scenes when you two are together, you fight a lot (otherwise he can be quite blindsided by the request if you guys have been getting along).
As for the third ending, you need to be in the Pieto romance but not do as well with the missions. Try failing one and succeeding at one - this should give you the 'not best but not worst' ending for Pieto. If you have ending 2 then I am guessing you already did this for Bastien's romance, so it will be the same kind of thing that is needed.
If you would like more guidance on this or have any problems, please message me at support@blackcross-taylor.com and I can go into more detail there.
Many thanks for playing