Business cards are not English tests. They are meant to convey essential information and are subject to both space and stylistic limitations. We do things on cards we would not do in the classroom or in our other communications.
St with or without a period is a standard abbreviation for Street. Technically, a period (in American English) is the more correct, formal rendition. But it appears without the period everywhere, perhaps more often than with the period (at least on cards).
The directional expression NW is most commonly used without periods. Again, directionality traditionally used periods following the E., W., N. and S., but as a city locator, it has followed the state abbreviation pattern of capital letters without periods (e.g., FL, NY).
As to spelling out Street, I do it all the time, because I think it looks better, not because it is needed.
Back to Point One. Business cards have an important graphic component. They are a first impression and, unless the representation is confusing, distracting or ugly, do what you wanna do. Think different.