Okay, firstly, if your range is 1200-1550, (the lowest), why are you asking if exercise will allow you go "go over 1200"? YES. Every single day, regardless of exercise you MUST be over 1200. That is your minimum, not your ceiling, and consistently eating less than your goals would be harmful.
"Serving sizes" aren't that important. You'll get total fats, carbs, and proteins in the foods you track. If you find that you're consistenly over all goals, then your serving sizes are probably too large. If you're consistently under, then they're too small.
Start not by asking what you should eat or how much, but by tracking one normal week of exactly how you're eating anyway. That week of tracking will show you where you need to make changes by what values are out of range.
Deb, in New Zealand