It is legal for Legacy. In fact, it would be legal for Standard if you got rid of Wormfang Drake. If you look at the bottom of the Set column, it says "Legacy" so you can use that to confirm it is Legacy legal.
To be honest, you will be destroyed in legacy if you bring a standard deck to a proper legacy tournament, so I guess it is not good at all from a spike's viewpoint.
No, it is not. Certianly it isn't an issue to play with friends at the kitchen table or at the local store for fun.
Legacy decks that are played at tournaments have a very high power level, running playsets of the best cards ever printed, and tend to execute their strategies quickly and efficiently. Your deck has a lot of 1 and 2ofs, making it inconsistant (games played with your deck will be wildly different, while competitive decks try to do execute a specific plan every game.) Even the stronger cards in your deck have a very low power level compared to the cards competitive Legacy decks use.
As mentioned, your deck is standard legal without the Wormfang. You would have much more fun playing standard with it; your cards would be on the same power level as your opponents, though I do suggest finding more copies of the stronger cards, to improve consistency.
Legacy decks that are played at tournaments have a very high power level, running playsets of the best cards ever printed, and tend to execute their strategies quickly and efficiently. Your deck has a lot of 1 and 2ofs, making it inconsistant (games played with your deck will be wildly different, while competitive decks try to do execute a specific plan every game.) Even the stronger cards in your deck have a very low power level compared to the cards competitive Legacy decks use.
As mentioned, your deck is standard legal without the Wormfang. You would have much more fun playing standard with it; your cards would be on the same power level as your opponents, though I do suggest finding more copies of the stronger cards, to improve consistency.