The nutrafin co2 is no different to DIY co2 made from a carbonated drinks bottle. It could work if you used 2 or 3 bottles and changed them at different times to keep it stable. Connect them with a gang valve and use a drop checker and it should be fairly stable and give you a good co2 level. But then again it may not, im not sure if yeast based co2 would work on a tank that size.
If you can afford 70-100 pounds id go for a pressurized fire extinguisher setup, but i understand you may not be able to do that. Hopefully someone with more experience will be along soon to help you further.