The software I used to put together this panos is ArcSoft Panorama Maker... I noticed that when it works in automatic mode it does a really great job, but if it doesn't recognize the right stitching path it's very hard to correct it in manual mode
About the focal length, as I stated these are mostly random shots, and that means I wasn't caring too much about what focal length I was using or stuff like this, just I wanted to take the picture as I felt in that moment... anyways, the EXIF data for the photos tell me they were all taken at my lenses minimal focal length: 18mm.