First (because you asked)... I do not know for certain what the large thin brass disc is. The bit of "decoration" around its edge indicates it is some sort of ornamental item, such as a horse-harness ornament.
Thank you for making and posting the new photos. They show that all three of those bullets have a flat solid base, which is an important ID-clue.
Unfortunately, I need some more photos. Please make some additional ones showing bullets #2, 4, and 5 from a "90-degree sideview." Meaning, put the bullets on the very edge of a tabletop and lean down to take the photo with the camera held perfectly horizontally (not at an "overhead" angle). And, please show a different side of the bullets than in the previous photos.
Also, if possible, please try to give me a count of the rifling-grooves on them, if you think you can get an accurate count. (The 4 grooves on bullet #3 were the key to identifying it.)
And, please use your digital calipers to give me super-accurate measurements of the three bullets' exact diamter, and length, in hundredths-of-an-inch.
Here's a photo as an example of a "90-degree sideview." (I'll also include a baseview photo.) It's a US Army Model-1874 Colt .45 Revolver bullet, made by the Frankford Arsenal. Your bullet #2 may be a slight variation of the bullet in the photo, with the difference due to being made by a different manufacturer.