You're not going to be able to hide that much blood underneath the actor, so unless you plan on using an expensive dummy, I'm guessing you'll have to pipe the blood in.
A long segment of rubber or plastic hose would work pretty well if the blood isn't mixed too thick (and you won't want to be, if you want it to pool quickly). Run the hose underneath the actor and place the open end wherever your wound is going to be. Figure out a way to pump the fluid and you've should have a controlable pool of blood.
You might have a hard time hiding the hose for your long shot. You may end up hiding it under the actor's leg or some furniture. If you don't want to do either, you could run the hose under the carpet (if there is carpet in the room).
That's how I'd try it, anyway. Hope that suggestion helps, or helps spark an even better one. Cheers.
