Hello there,
first of, I wanted to say this is one of the best job descriptions I have read in a long time on freelance networking sites. Its precise enough so there are no further questions to ask.
Before I start blattering about my offer, I care giving you some advice concerning the use of keywords for your long term blogging success.
You should NEVER overdo it. Google has become really good at spotting SEO optimized content and slapping it, treating it as spam. However, if you aim for quality and natural sounding content that is appealing to your readers without worrying too much about keywords, you're not at risk.
Besides of that, wordpress cms is a really good choice if you are starting out with your project.
Plus, there are a ton of nice free plugins that can automate almost 80% of your SEO efforts and therefore save you a lot of time and money.
Now considering the actual job offer, I could provide you with a keyword matrix based on your existing 500 words. That way you can dispose of all high value keywords relevant to your niche, including synonyms and related keywords and use it on a long term.
Of course you still would have to update this matrix from time to time as search behaviour and intent vary over time.
This could be done for you within 2 to 3 days
At least, thanks for considering my application.
Even if you decide to go for someone else, I'll make myself a pleasure helping you out if you need some advice.
best regards
Sebastien