Domain Authority is Complicated
As @Zistoloen has mentioned in a comment Domain Authority is much more complicated and everything you have listed as far as I know will not improve your domain authority unless your other domains have good authority which would pass it back.
You should look at Domain Authority as how much Google trusts your site and how important it believes that the pages you add are, the more domain authority you have then the better chances your pages will be found within the results higher up, but please note you also have page authority so a site with low domain authority could have many high ranking pages because they have good page authority on some of there pages because of several factors.
How to increase Domain Authority
It's important to note that no one truly knows the metrics that Google uses to establish domain authority but from studies from sites that are clearly authority we know certain things. So here is some ways you can increase domain authority:
Off Page SEO
Back links can help your page authority but they also increase your domain authority but they can also have a negative effect which I will explain in a moment. Basically you can increase domain authority by obtaining 'Quality Links' now what I mean by this is if you have 100 links from just random blogs then your domain authority will likely see much improvement in terms of authority since the domains that are linking to you are low in authority value. As will web design saying less is more, this is the same principle when it comes to back linking.
Let's pretend you have a website that is about rabbits, a link from a well know animal charity is likely to be worth 100-1000's of links from blogs purely because they are trusted and this should pass (Remember, this is not official - but what we SEO'ers believe).
Generally if you want to increase your domain authority via off page SEO then it is believed that you need quality links but its also important to be aware of Evil Penguin so below is not only how you can increase domain authority using off page SEO but also keeping your link diversity in good order so that your domain authority receives no negatives via Penguin:
- Keyword Anchor Links:
<a href="#">Rabbit Food</a>
- Site Address Anchor Links:
- Sitename Anchors:
<a href="#">Rabbit's R Us</a>
- Branding Anchors:
<a href="#">Rabbit's R Us - Hay Pellets</a>
- Site Address Mentions no Anchors:
- Sitename Text Mentions:
<div>Rabbits R Us are cheap etc.</div>
- Branding Text Mentions:
<div>Rabbit's R Us - Hay Pellets.</div>
- Article Mentions/Links
- Comments Mentions/Links
- Social Media Mentions/Links
- Forum Mentions/Links
- Citations Mentions/Links
- Footer (Site wide)
- Below the Fold (Within the content)
- Aside (Divided from content HTML5)
^ This is very debatable but we do know that Google now doesn't take to nicely to site wide links if the content is not relevant. i.e computer shop linking to rabbit site makes no sense.
Many people believe that only follow links matter, this is simply not true, while its believed that follow links pass more juice nofollow links are just important for keeping your profile in check, its hugely unlikely to have 100 links follows and 1 no follow. Generally these days sites should have more nofollows than follows for a natural profile since so many sites that link out are nofollow.
Google has said that the type of links you want are those that are relevant to your own niche, for example if your site is about Rabbits and you get a link from a site that has huge authority in car manufacturing then its unlikely that kind of authority will help you.
It is believed that a domain that ages receives more domain authority over time, its like actual real world businesses, they become better over time and more trusted by their customers (well you'd hope). So this is why many opt to buy aged domains because they already have the authority and they are generally easier to rank faster.
This is hugely debatable since many old sites that have not been updated for years rank super easy when they do finally get around to updating their site, but in all honesty the logic behind this having a role in improving your authority is that the more fresh content you have on your site on a regular basis that is 'Quality Content' the more chance that at some point you will receive those golden links from sites that have really good authority, so indirectly I would say this improves your domain authority. Please note that its believed that Google also separately increases rankings for sites that are constantly updating their site via new articles or freshening existing but there's no evidence or official word as far as I know that this directly has a role.
Please note: A lot of the advice in this answer is unconfirmed and you will not be able to find a lot of this mentioned by any official Google employee simply because they do not want people attempting to manipulate search results, you should always take such advice with a pince of salt and make what ever you want to make off it and make your own discussions what is the best approach for increasing your rankings.