The distortion problems are exacerbated at the wide angle end - which is what you need for interiors. If it was me, I'd at least expirement with using a lens with limited distortion and stitch a multi row pano. As long as you have a pano rail that let's you rotate around the entrance pupil you won't get parallax. If you shot portrait, depending on the lens, you might not even need multi row. If you wanted to get really fancy you could duplicate the panos at various focus points and combine in Helicon focus to get as much dof as you want.
Having said all that, the only problem that really jumps out of the second image is that the right hand window frame isn't vertical. In image, transform, distort, you could pull the bottom right corner out a bit and that would solve most of that problem. I actually find the distort tool more useful for perspective correction than the "perspective" transform option. As for barrel, or pincushion the lens distortion filter seems to work OK but for mustache distortion, if that's a problem, I don't know what the solution is.
