I really would not Expect... anything or any reaction from his Dad.
He is the way he is.
Everyone is different.
If you keep letting your Fiance's Dad's personality.... bother you, or you try and make him please you or try and change him or try to keep saying how you wish he were different, then it will really cause problems.
And with your relationship to your Fiance.
He is just a different personality from you and your family.
Let it go.
You cannot make... everyone....excited in the exact same way that you want them to.
Everyone has a right, to be who they are.
And if seems that your Fiance's Dad is not a mean yelling loud spiteful man. He is just "boring" and low-key and non-communicative as your Fiance said he is.
Just accept that.
Or you will CONTINUE to have problems, with your Fiance's Dad even after you get married. Why make problems? This is just a problem of your not understanding another person's self-expression or lack there of.
Not everyone will dance up and down and have constant excitement about someone else being pregnant.
The thing is: your Fiance's family is different than yours. And your Fiance and his Dad... were NOT close. So don't expect this relationship to be like you and your family's.
If you are always "disappointed" in your Fiance's Dad... and your "expectations" of him are always different than who he is, then you will always have problems with your Fiance's Dad. And then your Fiance will probably start to have problems with you about his Dad, too.