First, I just want to throw out the disclaimer that I approach these question from an Aristotelian-Thomistic point of view and my proficiency is moderate. There may be other legitimate ways to approach these questions.
You're right about this. I was trying to wrap my head around it as I waited for a response, and I started catching myself doing these things.
Good, I'm glad you see it!
How can we say time had a beginning if there was no before? And how can we say time has an end if there is no after?
There are different theories of time. An Aristotelian theory makes time the measure of movement or change. Thus in order to "create time" God would not create a subsistent entity called "time," but rather would create a subsistent entity subject to change, such as a grain of sand. So time is co-existent with any entities subject to change (or material creation, which can simply be referred to as "creation" for our purposes).
The beginning and end of creation are relative with respect to creation (although there may well
not be an end, as it would require an annihilation parallel to
creatio ex nihilo). So to say that there is a beginning to creation (or secondarily, to time) is a reference to what follows: the whole or continuation of creation.
Oftentimes a beginning implies a change--it implies the end of something else. Thus the beginning of the frog is the end of the tadpole, the beginning of Tuesday is the end of Monday. Thus beginnings
within the temporal realm signify transition or change. Yet if we wish to speak of the beginning of creation--of the temporal realm itself--in a way that is not just a reference to what follows upon the beginning, we must acknowledge the fundamental difference from beginnings within the temporal realm; we must recognize the
sui generis nature of
creatio ex nihilo. It seems to me that your question does not recognize this.
You ask, "How can we say time had a beginning if there was no before?" You mean to say that beginnings always imply a (previous) end, a change, a transition, a before. But that is a mistake. It is only true within the temporal realm itself. It is not true with respect to the temporal realm as an entirety. Strictly speaking, a beginning implies a middle and an end, but not a before. Thus creation is not situated contextually: it is not situated in a temporal, spatial, or any other context. It is, of itself, something entirely unique, something which as a whole has no relations to other created realities. It is unmoored. There is no before. There is no reference point. Reference points only begin with creation.