Getting married with a b2 is not the smartest decision, that's why we have k1 and cr1 visas. Have this in mind cause this situation may raise some eyebrows during your AoS interview. Anyways, you current status is B2 visa holder. K1 visas and cr1 visas ( fiance and spouse visas) have this numbers, that's why they are asking them. If your current visa doesnt have a RED numbers you should leave it in blank.
And yes, you are an immediate relative of a US citizen
