Dry Den? I've used that before for my rabbits.
For his age, the picture when you first got him, he looks about 6 weeks old to me. But if he was a runt, that could make him look younger than he is.
For determining ***.
https://rabbit.org/how-to-determine-a-rabbits-***/
http://www.rabbitnetwork.org/educat...rabbit-care-articles/how-to-***-your-rabbits/