Would I be ruining my SEO work if I begin to publish blog posts for the same keywords that my content pages target? Am I basically forced to find alternative keywords and only target one page per keyword?
In short, yes.
When Google provides search results they need to search trillions of pages to determine which result is most likely to satisfy a user's query. One of the key components of their algorithm is relevancy. If you have a page titled "chocolate ice cream" and then a blog article with the same title, which result should be returned to a user who searches in Google for "chocolate ice cream"?
If you offer multiple pages with the same keyword focus you run into an issue called cannibalization. You can solve that issue by narrowing the focus of one of the pages. For example, the main page on your site is what I would refer to as "evergreen" content. 10 years from now someone can read that page and the information is likely still valid. Your blog often offers fresh content which is more time sensitive. Some possible topics for an article:
Top 10 Chocolate Ice Creams in the world
Lowest Calorie Chocolate Ice Cream
Chocolate Ice Cream Recipes
I would also recommend being very careful when providing content on two similar keywords. It takes a level of expertise to do it in such a way that it adds value to your site. One helpful step is to use anchor text. If you write an article on "Chocolate Ice Cream Recipes" then one time in the article when you refer to "Chocolate Ice Cream" present it as an anchor link to your main page.
