The warnings are 8-14 and 5-8 words respectively, and state the case concisely. The word "risk" appears nowhere, and is a common English word anyway, and "vulnerable" and its derivatives are also common English words.
How would you rephrase the warning in fewer than 8 words that would have helped your stepfather understand the problem and how to deal with it?
How would you rephrase the warning in fewer than 8 words that would have helped your stepfather understand the problem and how to deal with it?