I don't think it's cool for him to ignore you to the point of ignoring your text messages, but I also think you should be considerate of the fact that he does have priorities outside of your relationship. One of my closest friends is dealing with a very similar situation where her boyfriend is extremely oriented. Before him, she was in a relationship with a guy for almost four years. The guy was kind of clingy and always available. Always there, ready and willing to spend time with her and do things for her. She was also extremely close with his family. She got spoiled emotionally by that relationship. That relationship gave her expectations of what a relationship is supposed to be, making her believe she should ALWAYS come first. So with this new guy, I hate to say it, but she bitches, is mean to him, and gives him hell if he chooses to spend time with her family more than her. She thinks she has a legit reason to be upset, and maybe at first she did, but the way she handled it makes her look like an over aggressive brat. Now his family hates her and there is tension in their relationship. I love her to death, but I've even had to tell her; she looks whiny and annoying when she gives him all this sh*t for not putting her first and choosing to spend time with his family. Even though his family closeness is overwhelming, her method of handling it is just awful.
Damn, that was a lot of typing! : / I just wanted to share that with you so that you know how NOT to tackle this. I think you have a legitimate reason to be upset. Family first is kind of a selfish, unfair way of dealing with things when you're in a relationship and he's taking it to the extreme. Don't let his cousin crash on the couch. This is a special trip you planed months ago for you and him. Not you, him, and his cousin on the couch lol Stand your ground and tell him no. Tell him "I know you're really close to your family but this is where I have to draw the line. I'm not saying you need to always put me first, but this is just unfair." The whole food poisoning thing is really f***ed up too. His behavior is not cool, he needs to get it together.