Site architecture, inner link strategy and duplicate or thin content HELP :)

[insuretheheroes.com]

Ok, can I just say I love that Moz exists! I am still very new to this whole website stuff. I've had a site for about 2 years that I have re-designed several times. It has been published this entire time as I made changes but I am now ready to create amazing content for my niche. Trouble is my target audience is in a very focused niche and my site is really only about 1 topic - life insurance for military families. I'm a military spouse who happens to be an experience life insurance agent offering plans to active duty service members, their spouses as well as veterans and retirees. So really I have 3 niches within a niche.

I'm REALLY struggling on how to set up my site architecture. My site is basically fresh so it's a good time to get it hammered down as best as possible with my limited knowledge. Might I also add this is a very competitive space. My competitors are big, established brands who offer life insurance along with unaffiliated, informational sites like military.com or the va benefits site.

The people in my niche rarely actually search for life insurance because they think they are all set by the military. When they do search it's very short which is common as this niche lives in a world of acronyms. I'm going to have to get real creative to see if there are any long tail keywords I can use as supporting posts but I think my best route is to attempt to rank for the short one to three keyword phrases this niche looks for while searching.

Given my expertise on the subject I am able to write long 1000-5000 content on the matter that will also point out some considerations my competitors dont really cover. My challenge is I cant see how this can be broken into sub topics without having thin supporting content. It's my understanding that I should create these in order to inner link and have a shot at ranking. In thinking about my topic I feel like the supporting posts can only be so long.

Furthermore, my three niches within my small overall niche search for short but different keywords. Seems I am struggling to put it all into words.

Let me stop here with a question - is it bad to have one category in a website? If not I feel like this would solve my dilemma in making a good site map and content plan.

it is possible to split my main topic into 3 categories. I heard somewhere you shouldn't inner link posts from different categories. Problem is if I dont it's not ideal for the user experience as the topics really arent that different. Example a military member might be researching his/her own life insurance and be curious about his spouses coverage. In order to satisfy this user's experience and increase the time on my site I should link to where they can find more dept on their spouses coverage which would be in a different category. Is this still acceptable since it's really not a different subject?