The old round is just as good now as it was in 1885.
Maybe better, because we DO have smokeless powder. You fire two shots at a coyote or feral dog, or one shot signal your buddy. Perhaps one shot to evict a rattler from the driveway. You can wait until tomorrow -- or next week --to clean the revolver. Shoot even ONE black powder round, best clean it before bedtime, if you want to keep your handgun nice.
You have a difficulty with someone, you've more to worry about than pyrotechnics. A clear sight picture for a follow up shot may be VERY important. For cowboy action shooting, I really admire those so dedicated to tradition and authenticity that they'll do it the "olden days" way. But that's for contests, and for showing off.
If you accept the drawbacks of an SAA for self defense, there's a LOT of good loads. You ask about BP stuff, you either load or have a buddy to do it for you.
Save the RNFP bullets for sporting use and the JHPs for hunting. Obtain some 250 gr. lead semi-wadcutters and load with - -
Unique, 8.5 ----------- ~880 fps
H. Universal, 8.5 gr, -- ~ 840
Win 231, 8.0 gr ---------- 850
Do you believe the .45 ACP is a decent fighting cartridge? Any of these loads is better. You CAN load hotter, but these are plenty sufficient, and are highly controllable. None will numb your hand or slow you down at all. Concentrate on cocking, sight picture, and trigger press.
The Win Silvertips are a nice, soft shooting load. I personally believe in a full weight bullet, for whatever purpose.
Best,
Johnny