I've never posted here before but I was reading your posts and your situation seems so similar to mine that I had to say a few words.
My DS was also a poor feeder when he was younger - he loved food but couldn't seem to take in enough calories to gain enough weight. As well as the tube he had when he was a newborn in the NNU he had ng tubes put in at 9 and 13 months, both times for overnight feeds.
The tube he had in at 9 months stayed in for nearly two months and it never needed to be changed. The one at 13 months was a different story - he was a lot more active by that age and pulled the tube out by accident quite a few times. We took him up to the paed ward to have it replaced each time.
For my DS, having the tube put in was always quite traumatic. I don't think it was painful but he hated being held down. The nurses were always surprised by how badly he took it and I think most babies handle it a little better. Once it was in it definitely didn't seem to bother him at all. I agree with PP that the key is to make sure it's taped down well so that it is harder to be pulled out.
I'm really glad you got such good news in not having to take the NG path right now. If it is eventually something you need to do, my advice would be to pay a lot of attention to how you feel about it. As his parent, there is no one else who is more in tune with how he is coping than you are. It is very easy for the doctors and dietitians to focus on the grams and overlook the effect the treatment is having on you and your son's life.
THe pead was curious as to wether tube feeds over night might help him to grow a bit better/faster, but the Dietician believes that he is getting enough and that the tube might make him too full to want to eat breakfast, and create more problems than it would fix at this point.
That was definitely our experience. The overnight feeds worked well in terms of weight gain but caused some major problems with DS's eating which took the better part of a year to overcome. We would stop the feeds at 5am but up until about 11am he would be sick if any food or drink even went close to his mouth. With any luck your DS won't need a NG in the future but if he does this is worth keeping in mind.
I hope everything goes well for you and your DS. It sounds like you have a good medical team in your corner!
Best of luck