Thoughtful, well-argued OP premised largely on JW organization being 'up front' about its finances to back up their begging, did they? I can grant the GB were direct about the organization's claimed liquid financial state - but they didn't front up with an audited report of all their vast investments. Have the yearbook accounts of financial expenditure in the 'kingdom work' ever been seriously scrutinized? Moreover, speaking of the older possibly more loyal Witnesses dying off, untold numbers of them bequeath entire or large parts of their estates to the organization. Unknown is how much that alone gives the organization each year.
To the best of my knowledge, no insider with knowledge of the financial health - or otherwise - of the organization has ever defected and spilled the beans. Someone who 'should' have known, Ray Franz was notoriously tight-lipped about the organization's wealth.
Hence, as well argued as the OP is, it lacks definitive evidence about the veracity of the GB's 'disclosures'. I have never known the GB to ever disclose more than is ever fully expedient. I remain unconvinced their sanitized reports on JW organization were anywhere near the 'full' picture. This remains a religious organization steeped in secrecy, expediency and bottomless greed.
And, yes, I'd have to agree with others that your average JW is stingey in his or her generosity. I'd guess that had an astute Chuck Russell or Fraud- God Rutherford introduced tithing and coated it in Scriptural appeal, you'd never hear a pleading squeak about needing money. Or, given that all religions are 'snares and rackets', perhaps JW organization would be even more inclined to beg for little Sophie's ice cream money.