RE: Question 1: Funding Model

That some children aren't being adequately educated is undisputed. But that doesn't demonstrate that the cause is inadequate funding. The correlation between funding levels and educational outcomes is not that strong. In fact some of the districts whose student's academic performance is most troubling are funded well above the state average. (I got that $8,000 figure from a budget release by the governor from a couple of years ago.)

To determine how much an adequate education should cost, examine schools that are doing a good job and look for the most efficient. That will give an indication of what is possible in terms of good outcomes at the least cost to taxpayers.

While Prop 13 changed the source of education funding, I found the California Budget Project reported that per capita k-12 spending in California from 1977-78 to 2000-01 increased by 223% adjusted for inflation. It's worth noting that the beginning period coincides with a time where the taxes being collected were perceived to have grown so much that an angry electorate responded by approving Prop 13. Picking either peak or valley points in time for comparison skews statistical data. 

You're right that special education mandates have created a significant new expenses and they would lower the spending growth for the general student population.