Thanks much for highlighting them! I’ll try to answer them all explicitly even if they’ve been answered partially elsewhere.
I believe the intent is to require financial restraint, best summarized here by @mlphresearch after responding to @Dodger :
To which your next question is relevant:
My perspective is that they do not serve a legal purpose, but they could prevent certain kinds of abuse from happening compared to the other accountability requirements. The current requirements without a cap only require publishing past spending on a quarterly basis while these caps prevent future excessive spending. Of course many have argued that the current cap is not close to “excessive”…but the point is that the Zcash Foundation and/or the ECC would have to justify that position to the community proactively (e.g. “ECC would like a higher cap in order to support 5 more top-tier engineering hires, therefor we’d like to request the cap be raised”), rather than reactively. (e.g. “ZF spent $10mm last quarter to outbid Justin Sun in Warren Buffet’s latest charity lunch auction; it did not drive shielded adoption as much as we hoped, sorry”)
However, the downside here is if a legitimate, time-sensitive opportunity for large spending appears, it may be slow or difficult to raise the cap rapidly enough to spend money on that opportunity. So it’s a “more accountability vs flexibility/speed” trade-off. The Foundation is fine with either side of that trade-off (cap or no cap) but the ECC is not (although their rationale is less about this trade-off and more about how the cap prevents them from their preferred method of employee incentive alignment). I think that also answers your third question but let me know if not.