The aemserver user must be used to connect AEM with Campaign.To connect Campaign with AEM use admin or campaign-remote.To better debug this check on the logfiles in AEM what happens when you request the newsletters from Campaign.

add this dependency:        <dependency>            <groupId>javax.inject</groupId>            <artifactId>javax.inject</artifactId>            <version>1</version>            <scope>provided</scope>        </dependency>

How did you configure your external account in Campaign?

add this dependency       <dependency>            <groupId>javax.inject</groupId>            <artifactId>javax.inject</artifactId>            <version>1</version>            <scope>provided</scope>        </dependency> and make sure to use the 6.2 uber-jar

That is possible, please note that the archeType is not working on AEM62, you need to make a small change in pom.xml to make this happen.

Indeed Java7, however I don't if this is available prior 6.2And AEM6.2 requires Java8. 

I would look at the sightly text component (/libs/wcm/foundation/components/text/text.html)

It is recommended to have it enabled on publish. Most likely there is an issue in the JS-code that prevents the minification.

Can you disable minify, to see if this might be the cause.

Might be that you have a syntax error, and that the JS can't be minified..Do you have errors around minification?