My OH is on incapacity benefit along with a few other disability benefits, and within his claim he get £6.75 a week income support for me. I also receive carers allowance because he is unable to work.
Do you claim carers allowance for your wife? It is worth looking into.
I think (But I might be wrong, as my OH says I quite often am) that because you are married, the benefits office have to class your claim as a joint claim.
Did they say whether you applying for JSA would effect your wife's IB?
It may be worth you speaking to the CAB or your local welfare rights officer and they will be able to tell you exactly what you are entitled to.
Have you made a claim for any housing/council tax benefit you may be entitled to?