My understanding from the RRB, and from a married couple that I work with is the following:
You will receieve your benefit from his retirement minus what you get from your 401k
He will receive his benefit from your retirement minus what he gets from his 401k
You will both receive what your entitled to from your main normal RR retirement.
Your main retirement should not change based on being married to another railroader for the fact that your both paying the same taxes into the same system.
In any case, I'd call your local RRB office (and not the main number in DC as most of those telephone drones are pretty rude). Usually the local office's are pretty good. I'd also recommend sending one of those secure emails (its an option to send one to the local RRB office) and see what you get for a response.
RRB: (877) 772-5772
Secure email:
https://secure.rrb.gov/211.html