I don't check this forum that often - sorry I've been absent!

With regard to wind strength, it's very important that you have enough wind to right the boat. All the times that I single handedly righted my F18, it was blowing in excess of 15knots. My F18 weighs 399lbs.

Orientation to the wind is important and I usually drag myself in the water off the bow to rotate the boat. Then VERY quickly get back to the righting line and start to lean out hard. As the boat comes up, it will want to swing the mast and sails into proper orientation with the wind. I bet your problem is mostly the lack of wind when you've practiced righting.

with regard to downhaul, I've never touched it when righting. Take a look at the following picture (my old Nacra 6.0 on a VERY tiny and extremely puffy lake) - the sail has pretty good draft even with downhaul on.