The answer given in that question is correct. There is no C++ keyword equivalent to using() from C# because C++/CLI has deterministic finalization. When the object goes out of scope and there are no more references, it will be disposed.
You have 9 bits in your field and the default alignment of object code in 32bit architecture is word (32 bit) boundaries. So your structure item will be stored in a 32bit word. You could make it smaller by using a #pragma pack[^] statement.