expanding universe question

[Anomalocaris]

The balloon would represent the edge of the universe, the question was where does the extra space come from, that would be the air in the balloon.

No, the balloon itself represents the universe.
To get this analogy you need to completely forget about everything inside and outside the balloon.

There is no edge to the universe. For purpose of understanding how universe can expand, it might be better to think of space as not a thing, but a concept used to provide a mental analogue of behavior of things in space. Because space is not a thing, it need not come from anywhere.

Tell me if I am wrong, but it seems to me the reason why it can seem counterintuitive for things in space to behave as if all of space is expanding probably somehow boils down to this:

You subconsciously know energy is conserved. If things are moving apart as if universe is expanding, then the total amount of gravitational potential energy would have to be increasing. It is just like lifting an object in a gravitational field. You have to put in energy to move a thing away from the source of gravity. Where is this energy coming from?

Is this right?

If so, then the answer is actually quite simple. this energy doesn't come from anywhere because it is always exactly balanced by other forms of energy that has the opposit sign. Conservation of energy doesn't say any specific form of energy must be conserved. It only says total net energy has to be conserved. As gravitational potential energy increases, so does other form of energy with the opposite sign, the chief amongst these is dark energy. So the sum total of all energy in the universe remains conserved, no matter how much the universe and gravitational potential energy increases. Expanding universe and expansion of space has no effect on the net energy of the universe. No net energy is either added or subtracted from the universe as it expands. The only effect of expansion is things gets shuffled around between different buckets. So as nothing can come from nothing, nothing did come nothing.

Expandion of universe is just like a company taking on debt in order to buy assets. The assets keeps getting bigger, so you wonder where did the money to pay for all this come from. The money didn't come from nowhere because there was no change to net money. The company's debt is simply getting bigger in sync with assets. So the company's net worth remains precisely unchanged.

Think of god as a shaddy accountant running a company like that, and hoping to be on the make by tricking the market and hiding the debt, and you see how space can keep expanding.

Does this help?