2. Does it make sense to have other advertising on my site? Should I just stick with Adsense, positioned properly for good CTR?
I know banner ads are less effective and thought to replace the Adsense 468x60 banner with another network ad. This way, Google will not penalize the entire page for having a poor CTR banner ad.
3. This brings up my third question...does Google base potential earnings from the entire page CTR or by individual ad performance?
I could be reading too much into this and should simply stick with the ads that get good CTR and don't worry about filler.