Perfect pics mate. I am guessing that this guy came from your LFS? Now please don't take this in a bad light(as you have saved this fish), but that Discus needs some bringing back to full health. It does not look sick, just unloved
. Give it some good food to get some vitamins in its body and it will be shinny and bright. You can see that it's fins are a bit beat and it lacks some shine. This is nothing to do with you, as you have just saved it. I have done the same many a time. I have bought Discus I did not need just to get them back to health. So good on you mate
OK, let's get to it. It looks about 8-11 months old, and I would say it is a male. If you want to read about how to sex Discus you will see many keepers saying it is not possible, and some talking about pointy dorsal and anal fins. All true..... however, I have some close friends at a Discus farm, that has been in operation for 25+ years....... and they can sex Discus in a heart beat! I cannot, but I have asked them many a question. So here is what I know;
For sure many fully grown males have the very distinctive elongated dorsal and anal fin, which taper to a point and do not dissect the tail. However, males also have a dorsal fin that looks a lot like a cockerel hackle and starts further froward than the females dorsal.
Your Discus looks very male to me. If you can do your best to find a female then you will have less problems. Otherwise you will need at least another 5-8 discus, and you will be pushing your stocking levels with that many.
I am more than happy to share any knowledge I may have with you, but at the same time I am not going to dictate from a far on how to run your aquarium