Great job Nick. I was bouncing around several SEO and content marketing tools. I settled on SurferSEO and paid the annual subscription.
LSIGraph is another excellent tool for keyword research as well as finding latent semantic index phrases. It has a free keyword generator and a paid section for indepth keyword research for $11.00 a month.
Latent Semantic Indexes are essentially the interrelationships between words within a document.
Search engines and readers alike benefit from semantically related keywords. You may know that but I wanted to pass that on to your readers.
Cheers.