Technical astigmatism correction questions

A 37 years old man with congenital myopia and astigmatism finds that he likes the sharp image seen when he tries reading a book with +0.5sph -1cyl lense combination. Such prescription means that he has essentially only astigmatism correction applied without any additional + or - sph because +0.5sph -1cyl yields 0 spherical equivalent, right? If attempting to add more +sph addition, the person reports that reading doesn't feel that comfortable anymore.

1.
Is it a valid practice to prescribe reading glasses that only correct for astigmatism and have spherical equivalent 0 ? I'm just studying and I somehow I haven't yet found any example material where such cases are mentioned.
Are there any caveats to look for? Is it even worth wearing such glasses if they don't help to improve his reading abilities but only make it slightly easier for eyes to focus?

2.
This patient's distance glasses have -0.5d applied in addition to +1sph with -2cyl but he reports that circles and squares look unusually squished to him. As he doesn't wear the distance glasses all the time, he finds the transition between wearing / not wearing the glasses somewhat uneasy to adjust because of this squishing. Does this squishing mean that the cyl power might be too much for him and should be reduced?

Thank you.