As for what is faith and belief you can get a lot of meanings.
But there is a scientific belief. The one that comes with a deep rational process involving emotions, logic, wants among other things. You don't merely choose such believes. Thus, if you want to believe, but you find no reason to, you cannot truly believe. Not in a scientific way of belief, since you are not true on principals that come with it which require you to use to logically convince yourself. As you cannot truly believe because you are afraid.
On the other hand, you don't need any "special" faith given by God nor to believe without doubt in order to be a "faithful believer". Nor do you just have to hope or trust that your beliefs are true.
My understanding is that people believe in a lot of ways, for different reasons and perceive their beliefs differently. You cannot oversimplify and say that Christians are believing in this certain way and not any other.
That been said, there is nothing wrong of blind faith or believe without a reason. Or to believe just because you want to. In the contrary, they are must stronger beliefs. They are just too personal to be interesting to the rest. But there is also the kind of belief that you can reason with it, find the reasons and feelings behind it on one degree and see if they are reasonable to you.
If I explain my belief in a reasonable way, explain the reasons I believe in it, my feelings behind it, my thoughts and you still think that I don't truly believe, then you are just not being subjective. You are not accepting certain principles to judge a belief.
So going back to answering "if Christians believe in God", you have to use some principles to judge their beliefs. Which principles? Well, use more scientific ones. Which would be judging the irrelevant/temporarily reasons (i.e. believing because you are afraid) from the relevant reasons (i.e. believing because it is meaningful for you) behind a belief. Or use other principles that you generally use to judge any scientific belief.
Because I can agree that a (certain) little child that is afraid to say no to his parents doesn't truly believe, but not a (certain) professor in theology. Their belief is most likely not the same.
My point is that you cannot choose to be selective how you judge a belief. The same principles you use to judge a belief in physics you should use to judge a belief in a religion or an idea. That is being subjective.