Well, you have certainly done your homework! Your summary of the BCG treatment is GREAT....Think I will save it to use for other newbies!
As for the "pain" questions, the only real answer is that your mileage may vary....every one is a bit different. Catheter insertion...being female that wasn't a major problem for me. But most guys say (and you will probably be hearing from them) that it is bearable. They use a very small catheter, not like the one for a cystescopy that has to carry a camera, and they usually use a numbing gel first.
The "discomfort" ....I think this is a better word than pain...after instillation also varies widely. Usually there is very little for the first few times. Then the probability increases as the immune system gets kicked up and this shows that the BCG is working, which is what you want. The usual side effects are discomfort and much urgency during the hours right after treatment, and fatigue the day or so after that. You probably wouldn't want to plan to work or go out to dinner afterward on treatment days! I was fine the next day, except for the fatigue. It is also important to remember that the dosage used is not set in stone. IF the side effects become too much, the dosage can be significantly reduced without changing the effectiveness. It has been shown that even 10% of the beginning dose works very well. And the side effects are no where near what patients undergoing traditional chemo have. I was at 1/3 dose by the time my maintenance was over. Occasionally someone is very sensitive to BCG and cannot tolerate it, but this is rare.
We are very fortunate to have this treatment for high grade non-invasive bladder cancer. I am now 8 years cancer-free!
Best of luck to you
Sara Anne