Turns out my thoughts about my prostate issue were on the right track. The urologists agreed that the antibiotics I was taking were having anti-inflammatory effects, which is what caused improvements in my symptoms. They also agreed with my choice to do stretches for my pelvic floor. Stress reduction was a big, obvious component in all of this, and arguably one of the toughest to accomplish (but meditation is helping me - although I still have a very short temper at times).
Diet was something else which was recommended, although I didn't think it to be quite as pertinent. I'm taking a supplement before some meals to reduce acidity of the food before it gets digested by my stomach's enzymes. Reducing acidity at this stage is supposed to prevent it from eventually reaching my bladder and prostate through my circulatory system. Whether it's actually effective is not entirely clear (but has supposedly helped a large proportion of people with interstitial cystitis significantly before), so I'm going along with it. I do sometimes forget it.
So, the combination of stretching (which I've noticed has a positive effect every single time), Motrin (usually once per day), a specific diet, some prostate supplements, acid reduction (through the aforementioned pill - plus some baking soda which I also drink for exercise purposes), and stress control, I've definitely noticed improvements compared to how it was a few months ago.
The fact that I'm able to take 1 Motrin tablet per day (only one time, when I was more symptomatic, I took 2) is wonderful. I still have mild symptoms during the day, but it's manageable and I usually do not notice them. That's a qualify of life which is more than acceptable to me at the moment, even though I think I can do better.
Eventually I'd like to be able to stop taking Motrin altogether. Although I'm not even close to reaching the maximum daily recommended amount, I still don't want to rely on it forever. The only times I might consider using anti-inflammatories is when I'm at some special event or on vacation, where random symptoms might otherwise get in the way. On a day-to-day basis, however, I would prefer to not use it at all, and have little to no symptoms. That's my end goal, and I hope that with continued practice of the above modalities, I'll be able to get there within a year or two.
Progress won't be quick, but I'm going to carry on. It's already been a week and a half without the antibiotics, so I am hopeful.