Offset and Clean up

Thank you for the help in my last post, I managed to boolean difference walls with my curved roof, but i have these triangles that appeared after the boolean, I was wondering if there is a way to fix it or do I have to explode the shape and delete each one.

Also I am planing to have windows on my walls and have a thickness of 30cm walls. Is there a offset tool for my windows like the one on skecthup and also is there a extrude tool in which i could add wall thickness

also is a way to draw on a curve for me to do doors and windows