We have been dealing with this problem for 6 years, as a result of scaring from the cure for prostate cancer a decade ago, and the progression of Parkinson's. For us it wasn't so much overactive bladder, as failure to void completely. None of the drugs helped. I agree, you should get another opinion from another urologist. We resorted to intermittent catheterization, at bedtime ( a huge help), first thing in the morning and once or twice during the day as needed and always before we went out. If your dad is physically stable in the bathroom, he can learn to do this for himself--it doesn't hurt. Clean-up is simple, warm water and soap. By the way, I did this for my husband, but it got to be wearing because I was tied to his needs--caretakers need lives, too.
We used a foley for 8 months, but it is uncomfortable, all though bag emptying and changing from a night drainage bag to a leg bag during the day, really wasn't a problem. Maintenance is pretty easy. I even trained our housekeeper to change the bags.
Now he is using a superpubic which was inserted as an out patient procedure using dilaudan (that took about 24 hours to leave his system). The bag change and maintenance is the same as the foley, with the cath changed by the doctor ever month.
Infection is a potential problem in all of the procedures, but it is a risk if the bladder doesn't empty, too.
Discuss all with your doctor.