As Lord Palmerston said of the Schleswig Holstein question: “The Schleswig-Holstein question is so complicated, only three men in Europe have ever understood it. One was Prince Albert, who is dead. The second was a German professor who became mad. I am the third and I have forgotten all about it.”
It's much the same for torrents.
"Upload credit" is the amount of actual data YOU have shared. So you will get at least the amount of your file plus any more that is needed to get the torrent properly seeding. It is, in my experience, always quite a lot more. If people's torrent client grab parts from other seeders, you don't get credit for that, the other seeder does.
As long as you have your file available for people to grab, it is 'seeding' whether anyone wants it or not. Your client should have something which shows if a file is active. uTorrent, for instance has a category for that. You should also see upload/download speeds if you have the columns for those showing. That will show what is happening with you.
The number of times your torrents have been downloaded is not an indication of your upload credit. The torrent clients may have spotted a better connection and grabbed pieces from there.
Bonus points are given from a downloader to your torrent (figures in yellow). They are then allocated to your account automatically. They can't be earned other than by a downloader saying thanks on the torrent page.
Not everyone has enough points to give to every torrent they download. Not everyone wants to give them because it is the one part of the whole business where you are not anonymous. Personally I am always grateful if someone just says thanks.
Finally, if you can keep your torrent client open with the files you have, it's a good idea. As you say you will get the per hour credit. But it is amazing how often someone will suddenly decide to grab a file and you get more credit from them if you seed. I am seeding a file on another site which I first reseeded a month ago. And somebody started grabbing it a couple of days ago.
Somebody has just grabbed a complete torrent that I first posted some years ago.
Hope some of that helps