It is rather unfortunate that you sold your other clubs without realizing you couldn't use the master tier clubs. I'm not sure how they could improve that. Perhaps you can email customer support and they can work with you.
As to buying what you want, well, that's just how they chose to structure their products, that's their right.
...though perhaps if you *really* want to, they could allow you to buy clubs not in your tier, then simply not be able to use them until you reach that tier. :]
Also your average is 68.9 , just put up 1 or 2 more good rounds and you'll be a master anyway.