I wouldn't go beyond 2 levels deep on any sub-directory except on rare occasions when it's still a short URL. The directory structure does not matter so much for SEO if done correctly. However, with WordPress, the breadcrumbs, navigation and site-wide links will end up with poorly prioritized interlinking. This could be bad if you do have important pages in sub-directory structures such as yourself.
For example, your 1st level directory pages such as /guides/, /treatments/ and /social/ are cannibalizing page authority simply because they are linked to more (and in better positions) than your Men's Guide page is linked to. I recommend beefing up the internal links to the Men's Guide page and improving a lengthening the content on that page as you mentioned you plan to do.
Instead of linking to the page with the anchor "Introduction" use "Men's Hair Loss Guide."
It's a good idea to keep URLs as short as possible so that your keywords have the opportunity to appear in bold in the URL of a search listing. This makes the listing more attractive.
You may also want to consider placing the Men's and Women's Guide at the top level of your menu instead of the sub-menu if possible.
I've also noticed you have a lot of old content being indexed with a different website design, such as the About Us page. I'm not sure if this is intentional, but I would suggest migrating it to the new design or redirecting where appropriate.
I hope these suggestions are of some use. Feel free to get in touch if you would like to discuss this or more advanced SEO further.