I'm not sure if you have decided to cave in, but I'm warning you. DON'T DO IT. It seems like some cute tradition to honor your husband, but it's not smart. Your husband's ego is not worth the trouble your (maybe) future son will face. My brother, best friend, and cousin, and uncle were juniors. They've had so many frustrations with issues at the DMV, credit cards/scores, loans, mail, school, job applications. Most departments and companies do not recognize suffixes such as sr. and jr., even if they say they do. Also, it leads to cutesy nicknames that your son will never lose. An example would be my brother who was named Allen after my father. Dad is "Big Al", brother is "Little Al". My brother is 48, 240 pounds and 6 foot 6. Despite being intimidating, he still gets teased. My cousin, also a jr., is always refered to as "mini-me" by his father and is pressured to be just like him. Even if you nickname him "Trey" or "Tripp", like I said, children grow out of their nicknames. Eventually as an adult he will no longer like being called that as it will be confusing around friends and even in his career. Don't let your possible future son be one of those guys who has to constantly remind people what his real name is. It's very frustrating for every one involved.
Please, you are not being insensitive and your husband does not need to have his child named after him to feel a "connection". In fact, if your husband is excluding you from the naming process of YOUR child, than he is actually being the selfish and insensitive one. He sounds like he's not willing to share or compromise, and that is NEVER a good characteristic in marriage or parenthood. Besides, if your husband puts in the effort to connect with his child, he will be adored and never left out. Perhaps even at times he will feel more connected and favored than you. You can incorporate your husband's name if push comes to shove, but don't make him a jr.
On another note, naming your son after your husband can put yourself in an awkward situation if siblings come along. You'll have the daughter who is resentful or feeling insecure about her own gender because it means she can't share that "connection" with her father. She'll feel like the wrong sex, whether you like it or not. Then there's the younger brother who feels like he was ripped off, or born "too late". If your husband needs to have his son named after him to secure "that connection" with him, then how will he be able to have that with any future children? Will he just force you into pulling off a "George Foreman" and naming all of your children after him? How tacky and narcissistic! Seriously, naming your child and should take into account HIS(or her)'s best interests.
Just say no to the jr., hun. It's not a good idea, it really isn't.