What most P2P programs do is allow users to upload from you at the same time as you are downloading, so you are actually sending what you are downloading.It is possible to adjust you upload limit if you think too much bandwidth is being used, but most programs ask that your upload is proportional to your download, meaning that if you did lower your upload rate, your download rate will also be reduced.
I dont think your upload has any effect on your download limit, but I cant be 100% sure of this.
Sorry, but I do not know of any program that will monitor this for you, but I am sure someone out there can recommend one.