Self assessment questions

[Welshbeef]

Two questions
1. If you pay Maintence is it tax deducatble I ask as when I filled it in online one question was about Maintence or alimony payments

2. If you are married how do you actually go about declaring say rental income or any income not dealt with via income tax through payroll ie to use a 0% or 20% tax threshold v a 40-45%? My wife is 20% but will drop to 0% so want to take advantage of it.

Thanks