Maximum is 3 Ads on your blog,but for premium is not limit ,suggestion to place a ads is what google support say ,cek google support
Yes, there is a limit of Adsense ad units per page. Check it in Google policies. Ad Sizes for better CTR will very with your web site theme and layout.
Good friend, you can use format 6 times ads ( text 3 times +3 times links + search box), but I used less than 6 times. If you use more times ads, your earning will reduce and if you use top ads and you put lots of content on the webpage, then you have more chances to earn. I think static site is more better than dynamic or software script.
Maximum of 3 ad is allowed per page/site. My suggestion is to have 1 or 2 max which helps your users/visitors know you care about them too rather than you are money minded.