Unfortunately I don't have the software required to make a video. For the first VSS (from the picture it looks like that's the one you are refering to), the one used as the X-trajectory, if you have created the section and entered the relation are you getting a flat surface? If so check the options tab and make sure it is set to variable section. Jaques-Michel shows how to create it in his video. The only other thought I have is is that a construction circle or are you using a cylinder surface as a reference? If the latter, it appears you may have additional geometry (two lines) that is preventing a regenerable section. If the end points are at the center and the other on the circle as you have shown in the picture there should only be an angle dimension (sd3).
I should add that the method illustrated in the video creats a kind of distorted cut... just like having a Warp feature doing it instead. The cut is not circular. You can see this effect if you increase the amount of turns.
Going back to your original drawing there is enough information that the 7.75 isn't completely arbitrary. Removing the shank length the thread length is 279 (I assume mm). Defining the VSS through the ridge of the first thread and using the lead value you specified on your drawing, the ridge distance of the first thread is 48 mm in one revolution. If you you start at the first ridge the thread length is 278 mm. Dividing 248 by 48 gives 5.792 revolutions. Noticing that the thread doesn't go all the way to the end I chose 5.75 as the number of revolutions which is 276 mm in length. Because of the section I used I needed to extend the sketch for the origin trajectory so the cuts extend through the entire length. I chose to extend the trajectory 1 lead length (48 mm, 1 revolution) at each end so the number of revolutions needs to be 7.75 to make the lead for the screw correct. Another way to do this is to replace the 7.75 in the relation by the length of origin trajectory/lead length which should give the same value and you wont have to worry about updating the value manually if you change the length.
I can upload it again but it will be a couple of days before I can. I did try the files again and had no problems opening them. Another thing you may want to try in the meantime is select the file, right click, and choose explore. This should open the zip file in windows explorer and you should be able to extract the files that way.
I had to make some assumptions because not all the information you show in your pictures came through. When I initially opened the dwg you posted some information is missing when I import the drawing. Here is what I get. The 273 dimension does not show up. Although I could have gotten the dimension by adding a created dimension I didn't think to try that since there was no indication of scale.