you would be fine and comments above pretty much cover all... i think you just have to be prepared to be tired for the first few days after you arrive. with combination of nursing and white noise young babies usually do pretty well on flights, ours did, but when we travel with him now at 15-months it's another story!
wish i've known about ground assistance which would be helpful on the flights i took when my husband was not travelling along, esp for the trip to LA. we have been on 6 trips with our son since 5 months and half of those with only me & the little one. i thought it's only available for kids travelling without parents as well as elderlies since we always requested that for our grannies, as i went through that myself when young going to visit the grannies... i always pay for porter service though, coz it's just easier with dealing with the luggage until we get picked up, even people around would usually help.
our experience through security check and custom are usually positive, hong kong airport even has family with kids line now from our recent Christmas trip! i always prefer to check in the stroller and keep my carry on items light (my usual baby bag or a rollie luggage) so it's easy to go through security check with baby in the carrier. the only time i had to take him out of the baby carrier was in LA airport, had to put the carrier through the screening machine along with my bags, shoes etc so it was not fun travelling by myself that time without assistance, but all other i pass through the security check with him on me without issues.
about the stroller, you can wheel it all the way to the boarding gate, where they will give you a plastic bag for the stroller and take it from there and will store all strollers at the luggage area during the flight, the stroller should be waiting for you at the gate when you land. it's really personal choice here depending what your baby is more used to on taking the stroller to the gate or using a baby carrier on board. we use a bugaboo bee+ which has a good padded trasport bag that i prefer to check in as an additional piece of luggage, and not having to worry about our stroller being damaged.
and since you are breastfeeding, make sure you drink lots of water and keep yourself hydrated... i always bring along a water bottle for myself (it's ok to bring liquid on board / through security check if you are travelling with babies under 2, in all airports which i've passed in asia, canada and the states).
the flight is indeed much easier then the ground transfer portion, you mentioned your baby is not used to sleeping in car seat, are you planning to bring your own or your family will provide one in the car when they pick u up? for our first trip back to Canada we just borrowed one wherever we were, thinking that since our son usually sleeps well in our car in his maxicosi, there shouldn't be any major issue. however as the make and style can be quite different, he wasn't a happy rider in some of those and he had a meltdown in one of the longer drive from Vancouver down to Seattle which was not fun.
in addition to his favorite toys, blanket etc, do bring along his favorite CD for music on the car rides, and be prepared to make pit stops at various gas stations, family restaurants or event on the side of the highway along the way, we find fresh air always helped... and be prepared that the usually 3 hour drive can be 4-5 hours...
one more think i wanna add about being tired for the first few days is dealing with jetlag. somehow our then 5 month son was jetlag during our first long haul trip back to Toronto (same time zone as New York). he is a good sleeper and was sleeping through the night since 3 month, but was waking up every 2 to 3 hours at night and wide awake since 4 or 5 in the morning while we were in toronto, took about 4 days to readjust so we did lots of early morning walk and i must say mommie was really tired! but again we were visiting our grannies in their 90's so they couldn't be of much help, it will be a better situation if you have family to take care of the baby for a bit during the day while you catch up with some sleep it will be a much better story...
good luck and enjoy new england!