Hi, relax mate and don't be too hasty to accuse your scope of astigmatism. When checking for astigmatism you need to have the star/planet dead centre in the FOV, if it is slightly off-axis you get a false reading, also use a fairly high power. If after checking it you still get some astigmatism from the primary mirror itself then it must be mild and nothing to worry about because your description of what you could see on Jupiter seems to show that you have a good mirror overall, so sleep easy
. Enjoyed reading your observation notes by the way.
Cheers
Malc