i'm going to take your word for it, that what you seek is healthy fat loss. cause 125 at 5'4" (are you a guy?) is not really fat.
but to get to your questions -
1) you can stick strictly to fish and eggs, that's fine. i don't think you should do so out of a fear of fat, though. but there's nothing wrong with fish and eggs. both are high quality sources of animal protein.
2) there's also nothing wrong with non-fat Fage greek yogurt. mark recommends a very low carb diet to people, so to keep calories up, he recommends high fat products. it's a trade off between carbs and fat.
3) 'cardio' is a bit overrated for fitness purposes, but it really depends on what routine you're actually doing. fuel too. a big reason why long bouts of cardio are discouraged in the low carb world is cause they're damn hard to do on a low carb diet! which is not to say that i think long bouts of cardio are healthy.
4) there's no need to eat every 3 or 4 hours, or according to any clock. two big meals a day is fine. four small meals a day is fine. i prefer 3 square meals most of the time, but indeed, eat when you're hungry.
"dean ornish and dr. davis think the palmitic acid our bodies use for fuel while we sleep is poison if we eat it. zero-carbers like charles washington think the oldest fuel in our evolutionary history – glucose - used by organisms a billion years ago and without which the brains of modern mammals cannot survive for more than a few minutes – is an unnatural toxin if you eat it. both views ignore basic facts of medical physiology and defy evolutionary history." - kurt harris