Straight To PHD or work with an MA as part time professor?
This is an opinion question which is disfavored here. It is also a personal choice question which is also disfavored. 

But I would think, in general, that there are better ways to start out on an academic career than with such a position. Unless money is a big issue, my advice, if I were your advisor, would be to get into the doctoral program now and try to pick up a bit of teaching experience as part of it. 

But that is an opinion, worth just about exactly what you paid for it.