toomanylols that text is not really an apology it is a an excuse for why he thinks he is rude. But as powershowerforanhour says I bet if he were talking to the boss, he could magically control his reactions.
The text is basically saying make life really nice and easy for me so I can be chilled and not rude to you and if you can't do that well... " I don't think this is uncommon in people. If there was some way I could stay chilled all the time, I would welcome the knowledge. Right now all so can do is try to stay cool, get plenty of rest and exercise." So his being polite to you is dependent on him getting enough rest and exercise and staying cool. I could say the same for my 5 year old but I do hope he is going to grow out of that!
What does " I do want to be happy with you and I do want our second child, just as much as this one." Has he suggested he is not happy to be having another baby?
I think whether you include him in the holiday to Spain or not is totally up to you but before the holiday I would be laying down some ground rules about how normal people live their lives. If he can't get a drink off you without making a shitty comment, he can go and fix his own drinks. He must not embarrass you in front of your family, and if he does you will retort. Personally, I would simply speak to him as I would to a naughty child "If you are going to be rude you can get your own drink." I'd say it in a jokey way, but I'd let him get his own drinks from now on.
I think he is doing this on purpose to undermine you, to show you who is in charge and maybe also to show your family, BUT if this is an isolated incident then hopefully he will learn from it, if you make it clear that this is not acceptable. (But that text doesn't suggest he wants to learn something, he wants to pass the buck).
Hope things will improve, you don't need to fight for days over something like this, you just need to make it clear, I won't be spoken to in this way, I will ignore you if you try and belittle me again.
Good luck. 