http://www.collegeforalltexans.com/apps/CollegeMoney/ This is Texas official financial aid package calculator and recently I’m going to attend NorthLake College with its COA at $10655. After I finished calculating I got $9711 in grants and scholarship aid 
:). However my question is if this can be a really good estimator of FA package estimator? My mom and I only 2 in the household combined make below $24000 fed POV line at around $17000 in reality.
Very few colleges meet the full financial need of all applicants. North Lake College is not one of the colleges that does.
There is not one NPC for all colleges in the state of Texas. Try the NPC on the individual college web site.
I don’t know without running the calculator myself. If there is a calculator on the college site itself that would be better to use. But did you not yet get your aid letter?
Be aware of the disclaimers.
"This calculator provides only a rough approximation of financial aid
Not all students will qualify for all of the aid that the calculator indicates may be available."
But if that is all grant money you are in luck. Often packages will contain your student loan. So if it doesn’t you can fill any gap with it.