Your daughter's husband can only divorce her after two years apart if she agrees to it. Otherwise he'll have to wait for a further three years:
https://www.gov.uk/divorce/grounds-for-divorce
Divorce settlements can be extremely complicated. (AB's barrister, Barmaid, is the expert!). They can either come about through simple agreement or from a court ruling. Courts generally rule very firmly in such matters in favour of the children of the relationship, meaning that your daughter (as the resident parent) could be entitled to far more than a half of what he's got.