Try this: write the letter to Graf and cc the skate shop.
That way, the shop isn't made out to be the bad guy and the manufacturer has to make an effort to resolve the problem. We both know the shop should have already addressed the problem, but they didn't make the blades, they just sold them to you. The defects (rust, poor finish) are Graf's responsibility. The shop has made some good-faith efforts, but the blades are just poorly made, which isn't the shop's fault.
In the letter, say that:
. per the box, the skates should have come with a better blade than the Royal 2000;
. these blades have chronic rust problems despite being maintained properly;
. the blades don't "hold" their sharpening well, even with the use of guards;
. repeated skate sharpening hasn't helped stop the rust from developing; and
. the finish is bubbling and peeling, which may be cosmetic, but isn't acceptable.
Don't volunteer too many dates. You purchased the skates in August and the rust problem began even before you used them in October. You had to have them sharpened twice before they even touched the ice and have made a good-faith effort to use these blades, but you're very dissatisfied with the quality.
Make sure you include your boot size, boot sole measurement, and the Royal 2000 blade size. State you would like to make arrangements to have a better blade mounted on your current boots or the set replaced with the same model boot and a better blade since you find this one unacceptable.
Include the shop's name, address, and contact info (owner/phone/fax) and ask Graf to make arrangements for replacing either the blade or the skate set. You can mention that the shop has been closed, so you wanted to wait until they reopened to address this issue. (Honestly, I would have sent Graf a complaint letter months ago. The shop is just the middleman.)
I've been up since 4:30am, so this is just a draft of ideas.