For a 2L, I add 1.5 cups sugar, 1 tsp. baking soda, and (for about two week runtime) 1 tsp. Fleishmann's Active Dry (not fast rise), in that order. Then add lukewarm water to within 2.5" or so of the top, and shake the dickens out of it.
Almost nothing is critical, and I don't see anything wrong in your recipe. The only total recipe failure I've had is when I tried only 1/4 tsp. yeast in an attempt to get very long, slow production.
Rio 200, hmmm... Are you running CO2 into the venturi normally used for aeration? I have a Rio 50 used as a diffuser, and it does something weird. Instead of drawing in through the venturi, it pumps out. If the tubing is disconnected from the check valve, and held above the top of the water level, it'll shoot water a foot straight up into the air. It's enough back pressure to prevent any CO2 from coming out for a few hours when a new bottle is attached - during which time the check valve is locked tightly shut. If this is going on for you, it might take longer with the extra air space in your bottles.
Keep at it. Separate and test every part of the system individually. You will eventually find out what's going on.
You were spot on with the yeast amount, I upped my dosage and it finally activated. My set up is finally working and it's building up the pressure now to get to 1 bps, I'm at about 1 bp30s right now.
As for the Rio, I drilled a hole on the bottom, slatted intake cover and I'm just running the airline up into that. Mine didn't come with the venturi impeller adapter so that wasn't an option. I always thought the little outlet adapter you're talking about was just for that weird silencer thing that the pumps come with?
Thank you for all the help yesterday and today, I never expected DIY CO2 to be this much of a hassle! My final product was a 2L apple juice bottle, gatorade bottle bubble counter and my Rio pump. I managed to snap my check valve in half today pulling old airline off of it so i'm risking no valve right now