Hi, It's Dr. C. I can help you today. I'm sorry that your husband is having so much trouble.
For a severe UTI, the usual antibiotic course is 7-14 days and improvement is usually noted by the end of the full 3rd day of taking. So after 72 hours. It sounds from the wording of your question, that he has been taking it for about 2.5 days.
He should be drinking a lot of water and perhaps was told to use an anti-spasmotic or muscle relaxant medication along with the antibiotics to help with the symptoms until the antibiotics worked.
If not clearly feeling better by Monday morning, that would be more than 72 hours and he should call the prescribing doctor to let them know.
If a urine was collected for culture, a "sensitivity" should have been run to verify that the right antibiotic was used. That result sometimes takes up to 72 hours to come back. If the sensitivity shows resistant strains, he would be changed to a different one as per the sensitivity results.
I hope this was helpful. Please reply if I can clarify anything or add details. I hope he feels better soon.