My question involves divorce in the State of: Texas

My husband and I have been separated since right after Hurricane Ike..about 4 months....my house was considered a total loss...insurance paid it off...I received help from FEMA for a hotel..and money to repair the damage...I cleaned up the house enough to come back...and my husband was staying with his father..but has now moved into the hotel..because he says he can't live there anymore..for what ever reason...now the time on the hotel is about to run out and he is telling me he is moving back in here with me (barging back in here) against my wishes...we went and had a letter notarized several months ago stating he was giving me the house and custody of our son with visitation...and $200 for child support (just our agreement on that paper)...not much since I lost my job and vehicle because of the storm...Drive for a living..Can he just move back in? Is the notarized letter signed by both of us binding in any way? He uses my son as leverage and threatens to take him from me...and is now using the house the same way...he smokes marijuana in my house and around my son (8)and I do not want him exposed to this in any way...before the storm we were arguing about my husband not wanting to leave the house if we separated and he said I would have to leave...I called the Sheriff about having him arrested for the marijuana and they told me if they came I would get in trouble too because I was in the same house...how is this possible since I don't smoke...