Plants that can't be killed?
Lets see.... Algae, Duckweed, Azolla, wait you wanted attractive plants. hmm. ;)
I would say... Anarchis is the fastest growing plant I have. If it gets ripped up it could care less. It works as a floating plant.
A Close second would be hygrophila... The only one I have experiance with is hygrophila difformis because polysperma is illegal in my state. Then again, so is anarchis... so don't tell anyone. ;)
So.. you have Java fern already right? You could try java moss if your water isn't too tough.
Anubias is tough but it's slow growing like java fern... For your amazon sword, try putting some large rocks around the base. Also, instead of root tabs, If I was only going to use one type of fert I'd use a liquid. People around here like Flourish Comprehensive. It's probably the one I'm gonna buy soon.
Daylight t8s should be almost perfect- another option is maybe the lights are too bright? If everythings not in balance your plants won't grow well. If your tank is well-stocked then you don't need CO2. Go buy a fert if you can, and see if growth improves. If it doesn't, then try replacing the bulbs.
If you can't buy any ferts, then try taking a bulb out and see what happens. You have to have balance, but sometimes lowering the light levels is the easiest solution. *shrug*.
I originally had too much light in my 10G- about 20 watts. Now the surface is covered with azolla and duckweed it's almost dark. Plants are still doing well though. I just want ferts to make some of my plants red.