Suppose you ...........a lot of money , what would you do with it?
( have - had - would have - are having
Everyone should be alert to defend (oneself- himself- ourselves- itself)
-iOld Ali has got ( him – himself ) married at last!
These are examples of usage of "get oneself married". I suppose this is what can be a problem in the third sentence.
I am not a teacher.
In the second sentence I would recommend using "themselves" rather than "himself" (Everyone should be alert to defend themselves) because it covers both genders. If you say "himself" it sounds chauvinistic .