Don't let your boyfriend make you feel guilty! You are absolutely right about this. I would never let my 7 month old go out of town without me for ANY period of time. I was still breastfeeding both my kids at that age so it would have been a non-issue anyway. Why is it so important to your boyfriend that the baby be gone? Is it because he wants to spend more time alone with you? Surely that can be arranged without the baby being sent to another state.
You're not overreacting one bit. It's not surprising that you'd feel uncomfortable about it. Your responsibility as a mom is to care for your baby, not send her on vacation. I'd be uncomfortable with the idea of someone caring for her properly for so long when they are not accustomed to the continuous demands of caring for a baby. It's one thing to babysit for a few hours or all day long. It's another to care for a baby 24/7 all of a sudden. I'd worry about my baby being left to cry or fed food not appropriate for her or getting sick. I don't like the idea of people other than my husband or me making decisions about my children. Not to mention, I'd worry about the people driving her around getting in a car accident. I'd worry about her being strapped in the car seat properly. I'd worry about her getting out of her routine. Heck, I wouldn't even go on a road trip with my children at that age because it's a lot of work. Also, separation anxiety starts up around this age. Babies need their mothers. I know some people are ok leaving a baby this age and going on vacation themselves (I'm not one of them). But that's a bit different than sending your baby on a road trip where they're spending hours on the road totally out of their environment.
I would tell your boyfriend that YOU question having more children with HIM since his decisions regarding the welfare of your child are questionable. I'm sorry if that's harsh, but the whole thing about him getting angry about this is so absurd.