Perhaps you would know ... are there degrees of rape, ranging from sexual assault to [first degree?] rape, with recommended penalties, and is marital status normally mitigate against the rape so that, while still illegal, it is not as bad as [first degree?] rape?
I could only speak to NY law as rape laws will vary state-to-state.
There are "degrees" of rape under the law and the penalties/sentencing requirements and guidelines will vary state-by-state. In the rape laws that I've seen (and I'm no expert as I'm not a criminal lawyer) the lower degrees --like second and third degree -- are largely reserved for statutory rape-type crimes and lack of capacity to concent (e.g. someone who has a mental disability "consents" but under the law they couldn't give legal "consent" as they were deemed to lack the capacity to consent.)
I've never seen marital status as a mitigating factor here in NY, and I would hope that if it is considered a mitigating factor in any states it would soon NOT be as forcible intercourse with a spouse seems to be one of the most abhorrent forms of spousal abuse possible.