Quite simply, it appears you don't have a clue what you really want from the design.
job: escort aircraft carriers and battleships, important cargo, etc.
Built: modern time- 2014+
budget: $3.5 billion
threats: aircraft, subs, fast attack craft, missiles, etc
That doesn't really sum it up very well, nor does anything past that. If you really want to end up with something workable or at least plausible I'd take on-board everything said to you by people such as acelanceloet, Rodondo, JSB and myself.