Mrs Smith is naturally a positive person but, like Anne, employment and feeling useful helps her. Anne's reaction seems to indicate that she would not deal as well as Mrs Smith in the same circumstances and perhaps that Mrs Smith would have dealt better with a broken engagement

He almost certainly has Anne and their broken engagement in mind during this interaction. He has no idea what the consequences of this speech will be - Louisa's accident is a direct result of his words

This must be painful for both Anne and Wentworth, the period referring to was just after their broken engagement and here the Admiral is speaking of wives. Austen doesn't point this out - it's up to the reader to "read the room"