I'm not a doctor, but none of these symptoms sound like hemangio. There are three types that I'm aware of, skin, which obviously you see on the skin, cardio which would cause shortness of breath and tiredness, and splenic which you usually don't find out until it's too late. My Brindle had splenic. There are many others on this board that have had the other two as well.
While it could still be cancer, it just doesn't sound like hemangio. An ultrasound will be able to rule out a lot.
I'm not a doctor either, but this doesn't sound like what I experienced with hemangiosarcoma either. I've lost two dogs to it and neither of them had any of these symptoms. Good luck and keep us posted.