yea so either way your screwed, so who cares, you get banned doing nothing wrong then consider yourself unluck and move on
You can increase page impressions by increasing traffic. How? There are to many methods and options for me to bother listing here. Just read what others posted in the forums.
Your ad placement and blending is very interesting and adsense shows relevant ads too. May be thats why you get that much CTR. But as you said it gradually decreases so you don't have to worry much. But at the end of the day if its still a high CTR then you need to start worrying.
You should not worry so much about that as long as You are not doing anything illegal( clicking own ads, telling your neighbours to click it and so on).It is normal for new site to have those kind of fluctuations and I do not think that Google is taking all that too seriously. Even if you get banned, it could be for some other unknown reason and only Google knows why( or maybe not)? Regards, Zgembo