Identifying wasteful spending is expensive and inaccurate. An auditor will produce some number of false negatives (remaining wasteful spending) and false positives (useful spending that was cut). Both of these cannot be zero, and the closer you would like to get to zero, the more expensive the audit will be.
Additionally, the relative value of false negatives and positives, in something with as high a force multiplier as education, seems like it will probably fall on the side of false negatives.
That is an excellent question. I carefully did not answer it because as soon as I do, no matter how wasteful and useless the program someone will come to defend it and I don't want to get in that fight.
Yes, but if you cut out the wasteful spending, you can redirect that funding to not wasteful things. What spending is wasteful is another question entirely.
If nothing else a tax break (even if it is only a few cents per resident) is a better use than some programs