Thank you.
As for the questions asked...
~No, I do not eat whatever I want, as long as it is under my daily calorie quota. You are doing absolutely nothing healthy for your body, if your 1600 calories a day consists of fat free pudding, fat free Pringles, a bowl of Froot Loops and milk, and cheeseburger.
Calorie counting (and WW Points counting) gives you the freedom of having no foods that are "forbidden" like on some plans, but with that in mind, any treat foods should be "treats" and not every day, or multiple times a day.
You shouldn't be eating the junk just because it is in your calorie range, or because it is reduced fat/sugar free-if it is still junk. The time for these treats are every once in MODERATION when you would normally occasionally have the real thing-and you want a slightly less evil alternative.
Say it is your birthday, and you go to dinner. You order one of the two low calorie desserts that Applebees offers-that is just fine. You had a wonderful treat on your birthday/anniversary/whatever-and you chose a better alternative than the full calorie/full fat desserts offered there and in other places. This was a great treat-but you shouldn't be going there and ordering their low calorie cake 3x a week.
There is a big difference in the freedom of having an occasional treat-and eating a good portion of your calories each day in junk.
~As far as my calories are concerned-if my limit were 1600, and I ended up having 1500 for the day instead-I wouldn't worry about it, unless I was hungry before bed, and then I would grab a piece of fruit or something to get it up a bit.
If I ended up though, at a really low level (below 1200) then I would make a point of having my evening snack/bedtime snack a healthy "mini meal" to get it up above 1200.