I'm unsure why an AdSense rep would suggest you label all your ads, unless it was decided that undue attention had been drawn to them. Normally, AdSense doesn't require a label above its ads provided your ads can easily be distinguished from other site content, either through appearance or sufficient spacing between the ads and the content.
AdSense ads are permitted to blend with your site's look and feel, provided they are not made to resemble content and mislead the visitor. Adequate spacing between the ads and your content must also be maintained. I make sure there's at least 2 or more spaces between my ads and any page content.
Also, Google warns against placing ads beneath a misleading header:
It's important that visitors to your site are not misled in any way and are able to easily distinguish content from Google Display ads. This policy prohibits placing ads under misleading headings such as "resources" or "helpful links". Publishers may only label Google ads with either "Advertisements" or "Sponsored Links".
Therefore, I never place ads directly beneath a header; otherwise, I'd need to label the ads as Google directs, and labels tend to kill any ad response.
Regarding the placing of 2 ad blocks in the left content column, Google removed the 3-ads-per-page limit a while ago. That said, a single ad is less intimidating to the ad-weary visitor. I only have 3 AdSense ads on my content pages, and they generate more revenue than when I had 4 placed. A very long page could accommodate additional ads, but I never found that it was worthwhile, so I place only 3. It's a case where less is often more, but you should test to see what works for your site.
All the best,