First, 3 of those uses of Vivify are shared with the Mana Tea build (since it too can TFT->Vivify every 30 seconds). As such, the benefit of Rising Thunder in this case is only 3-4 free uses of Vivify, or ~150-200k mana. Second, Rising Sun Kick costs 2% Base Mana, so you're spending 66k mana for those 3 resets. That lowers the mana saved to ~84-134k mana.
The same goes for your A and B comparisons. The total cost of A is actually ~270k mana, and over three iterations will total ~809k. B, assuming it's going to follow the same pattern as A, save with one iteration covered by Mana Tea, spends 297k each of the two times without Mana Tea (but with one TFT for a free Vivify), and with the 7 covered by Mana Tea spends in total ~767k mana.
So really there isn't a huge difference in mana saved in these scenarios, and where there is a difference it slightly favors Mana Tea.