/3/ - 3DCG

>>365140
Glad to see you still going on with it, i'd like to see it finished someday!
What you want is either loops all over to create additional geometry to cut door from or pic related.

Make a plane resembling your door, extrude inwards, snap those edges to the wall, extrude outwards, merge vertices. That's how i would do it at least. It's definitely faster then cleaning up booleans and you can use a cylinder to shape into door with ease.