You wouldn't be eligible for Jobseekers benefit since you won't be looking for a job. There is no such requirement for FIS though, so I don't see why you wouldn't qualify.
Your husband could indeed use your tax credits and he could claim homecarers unless your income is over 5,080 for the year in which case he could get a reduced rate.
I'm not sure how much notice your employer needs - you may also consider taking unpaid additional mat leave and/or parental leave. Best to call your HR section and check with them.