David Brown's marriage to Annie Craig was on 4.8.1926 and regd in Ballymena. If you view that certificate on the GRONI website (which will cost you £2.50) it should give you David's father's name and occupation. Also David's address/townland which may help with the search. If you post that information here, I'll try and find his birth details.
Can't help you with his death. That might have been registered in Scotland. Do you know where the body was found in Scotland and I'll look for a possible death?