Gambling is a serious concern and his untruthful behaviors as well.
There is help out there for addictive behaviors such as hypnosis and counseling but he will have to be willing to seek help. You can only encourage him and perhaps set some limits with him. Addictions are hard to break but not impossible. It just takes effort and willingness on the part of the addicted person.
If trust is an issue in this area and his lack of respect to you, you may want to do some soul searching to figure out what is in for you from this relationship.