To begin with, over-charging really isn't an issue other than your own comfort. It is possible to stuff 40gr of 3f into the 45 brass but it takes a drop tube and a compression die. The result will be a wicked recoil when fired.
I load a LOT of 45 Colt among other pistol cartridges with Black Powder. Using a 200gr bullet 25gr of powder will give you a nice boom and the recoil of about what a Cowboy load smokeless load does. That just happens to be the exact load I use for 44-40.
Keep in mind that you need to ensure that the bullets you are using have Black Powder lube on them. The petroleum based lube used for smokeless will cure you of black powder cartridges in a hurry, the stuff will turn to tar. Using a lubricated wad between powder and bullet can lead to powder fouling depending on what lube is on the wad, so finding bullets with the proper lube can make your life a little easier.
If you wanted to load "Gallery Loads" you could do so using round balls or
EPP Ultra Gamers. If you used round balls you would need to scrape lube into the mouth of the brass before seating the ball, in which case using a lube wad would probably be best since a Gallery Load has a substantial amount of filler on top of the powder.
I did a video a few months ago that is a step by step of making and shooting
Gallery Loads. It's pretty elementary, but it might give you some help.
Most people have an opinion about Pyrodex, myself included. But if you can't get the real thing, then Pyrodex will work fine, just DON'T weigh it!! When the day comes that you can lay your hands on real Black Powder, get as much as you can afford. Until then do what ya have to do to make smoke.
As far as cleaning is concerned, I personally don't dunk my SAA's in the sink. I use Ballistol mixed 1:1 with water and it melts away the crud when sprayed on and/or brushed down the barrel. I pull the action apart probaby every 300-500 rounds and give it a good cleaning, but the Ballistol mixture that gets into the action during regular maintenance will act as an alkaline grease and pretty much makes them trouble free until you get something in there that doesn't belong.
If you're like a lot of us who try loading cartridges once or twice, you will get hooked on this part of Black Powder in a hurry!!