If you're doing on-page SEO, you can't focus on broad match, you can only optimize for the exact keyword phrases you use on your site in H1 tags, titles, and all the rest.
You could try to find all the broad match synonyms and stuff them into your title and H1 etc etc but then you're diluting the SEO value for any given page by doing so. Best to focus on 1 or 2 keywords per page and optimize for that.
My suggestion is to take the large volume you get from broad matching, and find the exact phrasing that takes the lion share of that volume and go with that.
As Dan mentions you must be careful though... within a set of related keywords that broadly match a phrase, some keywords are at the beginning of the buyers funnel and others are at the end. Make sure your site is optimized to take people along that funnel. Don't only optimize for the biggest search phrases that only people not actually buying use.