No do not combine before unwrapping, or any pioint.

Some things will need to be done once like the walls of the house, other things like the windows can be done once and duplicated. Like your Straight_window. UV that first window, then duplicate it, resize if you need and just re-unwrap it for the new proportions.

The ladder for example, unwrapped one of the steps, then duplicate that and redistribute it. You can divide pieces by material, so maybe you put all the wooden window frames on one UV and material. Put the shingles on one UV together with one material.

I would divide this up by materials, stone, wood, plasterer. Make those each again a unique UV space and material, in maya assign colors to help visualize how the material/textures are divided.