The D classes are limited specialty classes. The D-64 specifically is for trades that dont fall into any other classification.
I had a client earlier this year that did water/fire/mold removal. As long as you are not "rebuilding" anything, a contractors license is not required.
Specifically... if you remove carpet, but do not re-install carpet, or if you remove baseboard, but to not re-install baseboard, if you remove damaged sections of drywall, but do not re-install drywall, you do not need a license.
I'd suggest for your specific circumstances, to send a letter to the cslb license classification deputy outlining the type of work you do. They will make the determination as to whether you should have a license or not, and which classification you may fall into.
Your passing law exam is good for 5 years. If they determine that you do not need a license, and down the road you decide to get a license for something that requires it, you wont have to take the law exam again.