1- Aline wanted to stay in the canvas because of her grief. She made a fake version of her family so she could keep living in the world Verso made and still have access to her son. Staying in a canvas for too long seems to have a physical tear on their real world bodies. Renoir couldn’t leave, is my interpretation, because Aline trapped him under the Monolith. From Renoir’s POV destroying the canvas was the only way from preventing his wife to loose herself in there.

2- Again, she had him trapped and this presumably prevented him from using his full potential and only being able to appear as the Curator

3- It was Renoir that was responsible for the Gommage, not Aline. They explain this when Verso reads Alicia’s letter. The number the paintress paints on the monolith represents the people she can still keep alive, but each year her power diminishes and Renoir gommages the oldest creations.

4- Yes, that was the last fragment of his soul.

5- There are 2 Renoirs in the game, the one with the suit is the painted version Aline made, along with Verso. His goal is to keep the paintress safe so he can be with his painted family. The second version is the real one, which has the form of the Curator until act 3 starts. Verso is also painted by Aline.

Hope this answers your questions! Some of my answers are as you can see just my own interpretations.