no, not ultra = max everything, + AA at 60fps at 1080p. A 770 can have a good go at ultra, but won't always be 60fps.
Also dayz frame rate is not limited by your system, but by the server interactions in many cases, but a good system helps.
Yes, but it depends: as someone said before, you cant max arma 3 and dayz out and expect them to both run 60 FPS. You CAN put arma 3 at high of even medium and get close to 60 FPS. But dayz might be difficult. Like someone else said (again) the performance of dayz really depends on how good your servers are. And I am just going to say the gtx 760 has been out for a year or so and wasnt even that powerful when first released. If I had a choice of buying a 760 immediatly or wait a few weeks to save up for a 770, then I would choose thd latter. I would sacrifice a few weeks to gain months of being a good card later on.
The bottom line is yes you can run Arma 3, but you would need to turn down some of your settings. Unless of course you want Arma 3 gameplay to be a series of beautiful pictures.