Toilets, Sinks, Showers, Tubs and Disposals - toilet problems

Maybe you can shed some light on this. I installed a new toilet about 2 years ago. I put everything together tightened everything down and it was good and snug. probably about 6 months ago we noticed that the toilet moves quite a bit. I believe ( not a 100%) that the flange on the floor was plastic with steel bolts on it. I tried tightening the bolts down but have had no luck. We also notice a slight odor at times. The toilet is above a crawl space so I can't get under their to look easily. I am assuming it's leaking a little bit if it smells. Anyways, back to the flange, if it plastic and something is broke under there, how would you repair the flange. is it something you can repair from above or would you have to get into the crawl space to remove. I am not sure what is available for parts to fix this. The house is older and has he old cast iron waste line. Any thoughts?

I would turn off the water line to the tank, flush the toilet, suck up the excess water in the tank and pull off the toilet (remember to disconnect the water line :) ). You should be able tell pretty quickly what your up against then.