Most definitely is the Meds you mentioned. The SSRI's do/can cause impotence. Don't know is diagnosis but there are most likely others available that won't have negative ED effects.
As far as the pain, it might be Peyronie disease. Nothing that will harm you, but look it up.
https://en.wikipedia.org/wiki/Peyronie%27s_disease
You husband may need to consider weaning himself off the neuroleptics and trying Testosterone Therapy instead.
If you research, you are likely to find these as side effects of the drugs he is taking.I Few exercises of groin area may help to some extent. You may ask him to do abdominal breathing, male deer exercise, kegel exercise,Sat kriya, Circulating awareness around microcosmic orbit.you may also consult doctors who have prescribed these drugs.