Hi Greg,
I am not a lawyer. For legal advice please contact a lawyer.
That said, you'd need to check your local laws but in most cases, no, I believe it is not against the law to use a fake name when sending an email.
If they become harassing or threatening you should contact your local police.
If you want them to suffer some consequence for their action you can try contacting their ISP. If you provide their ISP's abuse dept with the full email headers and prove the emails are coming from the computer belonging to the person you suspect the ISP may slap them on the wrist. Most likely no action will be taken.
I am not involved in your situation but on the surface it seems the best thing for you to do is laugh it off and move on.
-Raymond