If the Open Rate is that high (although you have a small sample), then it's usually a poor offer or a muddled offer.
Target 150-250 words with the following components.
To some, this will look familiar since I wrote a book about it called Story-Driven Outreach:
https://www.amazon.com/Story-Driven-Outreach-response-compelling-Foundation-ebook/dp/B09SW2F8JV/
As an aside, for targeted lists like you have, Open rates should be above 50%. Response is a little more tricky but I'd expect 4-6% on that.
Feel free to share the email copy so we can take a look.