An teleological and ontological question

In combating my response to premise 1, my opponent has challenged me to show one thing in the known universe that can exist without a cause. This would be impossible in one respect, since everything we have observed at least would seem to have a cause. However, I will provide an argument based on something we should be very familiar with by now. 2.11 An actual infinite cannot exist. 2.12 An infinite temporal regress of events is an actual infinite. If we agree with these above premises, then there cannot be an infinite chain of causes. There must be some "first cause." Therefore, by my opponent's own argument, things do not necessarily require causes. And if we are to accept my opponent's reasoning for why the universe must have began to exist, we can also apply the same line of reasoning to this "first cause." 2.11 States that an actual infinity cannot exist. My opponent says that it is my burden to show that an actual infinite can exist. However, this is untrue. My opponent is the one making the claim. It would be ridiculous to ask me to provide an example, because humans have no means by which to observer physical or temporal infinities. Do you really expect there to be data about infinite regresses of temporal events? It's obvious to someone who thinks for even a second that if these did exist, we would not have chronicles of them. My opponent is simply saying "I have no examples of them, so they CAN'T exist!" This is bad reasoning, especially when used with something we could not have data for if it did exist. My opponent then, for some reason, tries to argue against my statement that "If either an actual infinite or an infinite regress of events could exist, than an actual infinite could come about through addition." (yes, I used the wrong then) He then uses an example which has nothing to do with adding actual infinites or adding in an infinite regress of events. I'll spell it out though. If an actual infinite can exist, adding X + an infinite creates an infinite. If an infinite regress of events is possible, then simply adding something over this regress creates an infinite. Heck, to make it more simple, the infinite regress, as it goes from start to end, just add one for every step. You'll get infinite. I was simply showing that without premises 2.11 (and 2.13 through it), premise 2.21 does not work. If my rebuttal of 2.11 ends up invalid, then so does this. Since it doesn't matter HOW MANY of the premises are invalid, there's no use defending against this point, since it requires that I've already shown that 2.11 is a premise without valid warrant. So basically, I have 2 independent points. First, I have shown that by my opponent's reasoning, there must be a first cause (since an infinite regress of causes could not exist). To not be temporally infinite, it must have began. By my opponent's own arguments, this means that it must have had a cause, which it doesn't by definition. This is internal inconsistency, and an internally inconsistent argument cannot be entirely valid. Next, I believe I have shown that 2.11 is a presumptuous assertion. It has no valid warranting, since even if in actual infinite was possible, we would not be capable of observing them, due to our many finite limitations.