Welcome to Webmster World aphroax.

More ads is not always better. Ad revenue is determined by supply and demand, with constant demand, increasing supply will cause the price to drop. 15 to 20 users a day is not a lot of traffic. To make a living from Adsense alone, these days you need in order of 10k visitors a day. What this means for you now, is that there is most likely very little if any specific demand for your site. So adding more ad units will result in a drop in RPM and little to no impact on earnings. At this stage you should be focused two things
1- growing your user base
2- optimizing your ad placements.

By optimizing your ad placements, I mean you need to be sure that the ads on your page are in location where they are seen and being clicked on by users. Placing an add in a footer is probably not the best position. Mobile users are unlikely to ever scroll down that far on the page. So the ad will likely never be seen. AVV, Active View Viewable is an important metric, it can be found on the far right of the standard Adsense performance report. You should try to maximize that number and aim for at least 50%. It measures how many ad impressions are actually seen by the user (at least 50% of the ad for at least 1 second). If Adsense loads an ad in the footer and the user doesn't scroll to it, the AVV for that ad will be 0. If the ad is above the header and the user scrolls past it before it loads, AVV = 0. But placing the ads close to where the user engages with the page will likely result in a higher AVV.

Should you put ads in the content? Yes most probably. Should you add more ad-units to the page? No, not likely a good idea. Remember my point 1 "Grow user base", users typically hate ads. Overloading a page with ads and placing ads in obtrusive manner will likely guarantee that user will not be back. You will never be able to make more money by adding ad-units, you may earn a few pennies more but that is about it. To make money with Adsense you need users.

keep Mobile Ad Density in mind. Not adsense specific, but ads in general. On a bigger site, I would do 1 ad at (or near) top and 1 at at bottom of content. And stick another one in middle of content. 750 words is pretty short. If you put two ads within content, you are likely to hit that 30% limit.

I am in the camp to max out your ads placement (while optimizing for view ability and user experience). I disagree that you will not be able to make more money by adding more ad units, I have always almost made more money by adding units that are likely to be seen by users. Test the thesis on your own sites. But keep in mind when you plaster too many ads on a small new sites, it has the potential to hurt future traffic / repeat users. So in that sense, I would remove footer ad personally in your shoes. I will NOT add the ad before your content. But I will add 1 unit within content and 1 after content. The side unit is whatevers, as it'll almost never been seen on a responsive setup, but I would keep it personally.

Related information:
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official language:
[support.google.com...]

When ads on a mobile page take up more than 30% of the vertical height of the main content portion of the page, the result is a disruptive ad experience, regardless of whether these ads are text, video, or static images. This includes “sticky” ads and in-line ads.

The Better Ads Standard does not include video ads that appear before (“pre-roll”) or during (“mid-roll”) video content that is relevant to the content of the page itself.

Included in our interpretation:

The density calculation applies to the fully expanded article or content of a page.
The content portion of the page excludes site headers, footers, and any content recommendations (e.g., “related articles” sections).
Ads include either external content recommendations or mixed (i.e., internal and external) content recommendations. If a module links to a page on your own site, and the presence of the link is not paid for, then it is not included in the ad density calculation.

end of official language
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The hard limit on ad units has been removed by adsense a while back. But I would personally avoid stacking ads, like two 300x250, two 160,x600 side by side.