1. Dwarf sag will grow much faster under low light/tech conditions.
2. Co2 would be necessary if you wanted to get higher light plants. But the plants you mentioned would be fine w/o co2.
3. You can use rubberbands or cotton thread to tie anubias
Why are you stopping the dirt? It will get you better results then just eco complete. You can add a high quality root tab, but dirt gets awesome results with no co2 or ferts. (Check out "dustinsfishtanks" on youtube, all his tanks use dirt)