As dogs age they do not come into heat as regularly as they did when they were in their breeding prime, so it could actually be that she is in heat. The thing that I don't like is that she can't jump on furniture any more and seems to be having a hard time getting around in general, as you explain it. That could signify that the discharge you are seeing is from pyometra, which is a life-threatening infection of the uterus that is very commonly seen in dogs that are not spayed, and especially in older dogs that are not spayed. I would not wait until Saturday to get her to the vet because if this IS pyometra, by Saturday it could be too late.
The small bump on her belly could be a fatty tumor or it could be something to worry about, only a vet will be able to tell you what this is upon examination. I don't, however, think it's connected in any way to the bloody discharge.
The swollen nipple could be connected to the discharge, and again, it's impossible to tell what that is without examining the dog. I would get her to the vet ASAP, if you have to miss work, so be it, if this is pyometra that is causing the discharge, her life could be at stake. Again, I do not like the fact that her energy has slacked off so much, that says that she's not just out of sorts from being in heat, it says that she doesn't feel well, and pyometra will cause a couple of degrees of fever, which will cause them to act like that.
Please stop back and let us know what the vet said and how she is doing.
Ghilly