Q1. You can tilt the camera down quite a lot for taking the zenith and still cover the hole at the zenith left by the horizontal shots. You can check this by using the Panorama Editor window and dragging the zenith image down manually in the edit individual images mode, or you can go to the Image Parameters tab and set different pitch values for the zenith image until you see part of the hole appear.
Q2. The panorama will not bend to the left if you stitch it properly. I found some of the automatically placed control points were not on matching features because there are some repeating elements where it is easy to pick the wrong features (e.g. on the blind slats). Bad points can skew the panorama and the solution is to remove/correct any badly placed points. (Use the control points table to find points with large distance values). But your panorama may simply not be levelled. This only takes less than a minute to do. See the tutorial (including video) to which I have already referred you, i.e. http://www.johnhpanos.com/levtut.htm. You will find the vertical line points I used in the project file I uploaded. Again, you can find those points via the control points table in advanced mode.