Yes, it will help improve rankings if your content is lacking relevance. They are no where near as important of an influence on SEO as they used to be but are still influential. Think of them as in content title tags.

Each page should have a unique H1 tag that describes the pages content and contains the target keyword.

Google knows the difference and that is why they wouldn't give it the same value.

They are looking for other websites to link to your site on their own. No organic link is going to have tracking variables appended to it, meaning that the backlink was "self-generated". As such, your link value is discounted (especially press release links).

Is the quantity correct?

You just need to do some detective work in GA and see when/where the product purchases were logged. How many different people? Did they revisit the same page (as you mentioned)? Where is your conversion tracking code located?

There are so many questions/possibilities that it's hard to determine without actually going into GA, following the conversion funnel, troubleshooting on page analytics code and analyzing the situation.