Salim, thanks for those videos.
Roundhouse elbow strike: think of a roundhouse punch (hook punch) but with the arm tightly bent and striking with the elbow.
Downward sweep: Like karate's downward block (gedan barai) but with the hand open in knife-hand (tegatana, shuto) form.
You are correct about the spear-hand thrust.
When you put it that way, the Roundhouse elbow strike sounds a bit like my elbow cross or my angled elbow strikes.
For that Downward sweep, would you be striking the thighs with it or something? I pulled up a youtube video of a gedan barai and tried to picture it the way you described. Striking the thigh is about the only thing I can think of for it off hand.