If you want to use the breaker amp rating for "I" you can, and that would give you an extremely conservative circuit that will have acceptable voltage drop even during starting. But I think this is overkill, and its going to cost way more than what I think you really need.
I don't believe there are any code rules with respect to voltage drop, just some guidelines. I would use the nameplate * 1.25 in the voltage drop calculation and try to keep it under 3% (7.2V).
I think that 30A breaker requirement must be wrong. Perhaps if it was wired as a 120V motor, but that still seems too large. For a 5 amp 240V motor, I would think a 15A breaker would be just fine.
