Hi, A.,
Congrats on your new baby boy. As another military mom in the area, I know what the pediatricians at the MTFs here say, and I have to say, in my experience, they're completely nuts. The best advice comes from other moms, especially other breastfeeding moms, and you're getting some great advice here. The best advice is always to trust your instincts--so you've already said the most important things: that you feel letting your baby cry it out at this point is not beneficial, and that you don't mind him waking up once a night to nurse. So who cares if your pediatrician has a problem with his sleeping patterns now--she's not at your house every night!
First of all, nursing a baby to sleep is the most natural, comfortable way to give him security and safety and reassure him that you will always be there for him. Falling asleep can be terrifying for an infant, and 4 months old is really young to try to "train" your baby to do anything. He isn't "manipulating" you at this point, he's crying because he's scared that Mommy is going away. (FYI, eventually when kids do wean, the bedtime feeding is usually the last one they give up). Sleeping through the night happens when the baby is ready, and he's obviously not ready yet--he's telling you with that one feeding in the night not only that he might be hungry, but also that he needs to "check in" with you to make sure Mommy is still there. I have twin boys who are almost 2 now, and they didn't sleep through the night until they were about 7 months old, and not consistently until they were almost a year. A consistent, calm bedtime routine is a great thing to start at this age--at the same time every night, a soothing bath with low lighting, followed by warm jammies and a nurse is a great way to get your son to learn what to expect at bedtime. You might also try some lavender essential oil, either in the bath or on the bedding, or both. The other thing we did was to put the kids to "bed" in their swings, because the motion put them to sleep almost immediately. They slept in their cradle swings until they outgrew them!
Also, I always tried to hold the babies close to me as I leaned down to put them down, and kept them on the breast until they actually were already in the bed. And I put a t-shirt of mine that I had worn for a couple of days into the bassinet so they could still smell me when they were in bed. (I also slept them on their tummies, to my pediatrician's unending horror. And they slept on soft, comfy pillows, wrapped in blankies, with friendly stuffed animals so they wouldn't be scared and lonely in an empty bare crib. I think a baby is far more likely to forget to breathe and die of SIDS if he's left alone, flat on his back, unable to turn himself over and without any companionship to "cry it out" than if he's in a soft, warm place with a lovey to cuddle with.)
The bottom line is, you're doing great. You already have all the right answers for you and your baby in your instincts! I also want to mention there's a parent & tot group for military wives in the area, if you don't already know. Feel free to email me at ____@____.com if you would like information about it--it's a great way to meet other moms from Bethesda and Walter Reed. And remember, the most important thing is to enjoy every moment. My kids are almost two now, they self-weaned at 19 months, and they now go to bed with a bottle and a story every night with no problems. It's a huge relief to have a consistent bedtime, but it's also a little sad to know that they'll never again nurse themselves to sleep, cozy in my arms.