I was born a preemie, a set of twins.. I weighed 3 pounds at birth with multiple complications - heart, lungs, ect.. But, guess what? my birthday is next week and I will be 54!!! so your little man, like my Ollie(grandson who was born blind, with other complicatons , info in my PDA here on the board) are both going to be fighters in this big bad world..
You are an awesome gramma, I just know it..
Prayers for strength for your grandson to thrive, grow, and be the man that he was born to be.. Keep looking up, and things will just get better as you love on him, and he loves you back in his own way.