1) Two part answer
a)Prednisone can cause issues as it is a steroid which is converted into a hormone in the body, because you now have extra hormones circulating your body will decrease your regular hormone production which lower your testosterone. That can manifest as a low sex drive and/or ED. After you've been on it for a bit your doctor can order a blood test to check it out.
This generally should't be a major problem unless you are long term and you're prednisone dependent. If you want to go the natural route you can take up exercising or weight lifting. Both will naturally raise your testosterone count; weight lifting will also help reduce the loss of muscle mass caused by long term pred use. Even if you ignore your core and just focus on the glamour muscle it will help. Or you can get your doc to write you a script for it.
b) Sulfasalazine can cause issues with sperm production. There has been some concern if Mesasalazine causes the same issues because it is a very similar drug. The general consensus is no, because they are pretty sure it is the Sulfa- part that causes the problems and Mesasalzine doesn't have that.
2) there are lots of threads they started a giant thread
here, take a look through that to give you some ideas.
And finally I do not consider myself a reliable source for information on any subject, double check with your doctor for confirmation.