is there a way to make the mana bar 1 pixel wide/tall instead of 10 being the minimum?
It's not pixels in size, its what %age of the unit section you want it to occupy.
If you look around line 38 or GridManaBars.lua you'll see :
max = 90, min = 10, step = 5,
Change these to somethig like :
max = 99, min = 1, step = 1,
And you can have the manabar occupy anywhere from 1 to 99% of the frame.