If only you can contact the service provide and on compassionate ground they could forward all text to your email address.

Or get a hold on his phone and forward it manually as text from his phone to yours.

The service provider will provide this info only with a court order, you can use a program like bitpim(www.bitpim.org) to download to compter from phone, will need to physically have phone but will not leave trace that you did it on phone. No way to forward

If doing as Trendy-Bee sugested, don't forget to go to the section for previously sent texts. So you can delete what you just forwarded. But I looked into the manual, and there is no automatic feature for doing that. If it were e-mail, then maybe. But not text.