I have had these issues for years. After much trial and error I have developed some techniques that work well. I apologize ahead of time for the long explanations.
For the cracked arms (REMOVE THEM FROM THE TORSO, or you'll have them in permanent positions) I have a couple of jewelers vice grips. They are needle nose and don't have teeth. I use them to hold the arm after I apply a little bit of superglue. (If you are worried about them getting glued to the arm put a bit of wax paper between them and the arm. Before I apply the glue I use the tip of an xacto knife to pry the arm apart a bit. Add the glue and quickly remove the blade. Put them in the vice grips for about 30 minutes and when they have dried they are as good as new. If hands still slip, add a tiny bit of glue to the shaft of the hand and let it dry. Then rough up the glue with a glue with a needle file and you are good to go.
My work on the cracked torsos is similar to the arms. Pry the crack open add a bit of glue, quickly remove blade and put torso in a set of smooth (non toothed) vice grips. If done right it makes the torsos like new. I have done this with the arms in or out and as long as you are careful there is little difference.
As for the fading decals or ones that the metallic paint is coming off I do a few different things depending on my mood, how much I like the torso decal and what I am going to do with it.
If I want to get rid of the decal completely I don't use Brasso (my fiancee hates the smell), I use 600 grit wet/dry sandpaper with a small dab of 3 in 1 oil on the torso. Looks like a new blank torso when you are done. Also, you can remove only part of the decal this way if that is your goal. I use this to modify faces. I sometimes use the tip of a knife to scratch a bit off then sand. If I like the general design but not the faded bits I use permanent markers by Squigley (not easily found in US, but much better than Sharpie) and draw over it if just the black outline is fading. On the old 80's torsos with the shoulder plates, I have made a bunch with completely black shoulder plates and they look great, especially on a red torso. If the gold is just beginning to fade, take the arms, head and legs off and spray a light coat of ABC clear plastic varnish or polyurethane on the torso. Allow at least 24 hours to cure (I recommend 48). This will keep the metallic from fading further and give the torso a nice luster. I have also used artist grade gold leaf to rub on in place of the original metallic. This works well but needs the lacquer. Lastly one thing I have done a few times recently is bought the reprints of the old decal torsos on Bricklink (I don't remember from whom), cut out just the decal and stick it to the torso over the faded decal and then lacquer. There is a small rise where the lacquer is but the fig still looks and feels great. I still haven't figured a way to keep the metallic swords from flaking. I have a few ideas but can't try for a few months until after my wedding, when I hope to post a bunch of photos of MOC's and minifigs I have made but not had time to post yet. Hope this helps.
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