First of all, you mischaracterize what he said. He never used the word "finite". You ASSUMED that he meant finite and then said he is totally wrong based on that. What he actually said at the SLC Q&A, in response to a question about whether the Choedan Kal magnifies the user's power (see link below), is that "my understanding is that it is a reservoir of power. It is not necessarily a magnification. A very weak person with a very powerful sa’angreal is very powerful." So rather than magnifying the channeler's power, a sa'angreal seems to allow the channeler to hold a total amount of power. That is, a sa'angreal grants the same amount of saidar/saidin to the user regardless of the user's strength. In contrast, an angreal seems to magnify the power available to the user.

This would make sense given that Rand and Asmodean each got equal amounts of saidin from the Choedan Kal in Rhuidean. This is also corroborated by the actions with the bowl of winds when they gave the angreal to the most powerful channelers. Actually, this even makes sense of why Egwene could keep the sa'angreal during the Tower raid.

Think of every channeler as having a "hose" which allows them access to a certain amount of saidar/saidin. An angreal gives you more hoses of the same size (a multiplier). A sa'angreal gives you a really big hose (but everyone gets the same really big hose, regardless of how big their own hose is). A well gives you a bucket that you can stick your own hose into.



This is your second mistake. Even if the Choedan Kal did allow Rand the power to balefire someone back that far you are ignoring the fact that it would destroy the Pattern. He says "I just laughed...c'mon lets run the math on this." (As a side note, this is not the response you would expect if the notes indicated that this is what happens (remember he has a lot of ToM written, and knows how the series turns out, including the reveal of Asmo's killer)). Brandon says "I think that if you did that to the Pattern the ramifications would be so dramatic you'd see the Pattern unraveling hardcore at that point, it's like balefiring an entire city." This is the ramification of balefiring ONE person back ONE year. There was something like 100-200 people in the fortress IIRC. 150 people back 1 year is the same as 1.3 million people back 1 hour (150 people*1 year*365 days/year*24 hours/day = 1,314,000 people hours) and the same as balefiring 5,256,000 people back 15 minutes (the more realistic assumption for how far the strongest channeler in the world can balefire unaided). The Pattern may have unraveled under the strain of that many people being balefired back 1 year. Using your number of 28 years it would be like balefiring 147,168,000 back 15 minutes. This is more than all but six COUNTRIES in the world. The Pattern wouldn't hold up.

Remember that RJ said numerous times that we can't trust the characters to get everything right. Perhaps he has introduced elements on purpose within the books where characters have misunderstood how angreal/sa'angreal work. Even the glossaries and BWB have been wrong at times.