My difficult child used to get out of control violent when he had a lot of access to computers/video games/tv/anything with a screen. Really really bad. I had a bunch of people undermining me to the point it made me nuts.
I think keeping it at work is fine. If difficult child will only use it in the car and that is your limit, go for it. been there done that. Just make sure difficult child doesn't sneak out and break into the car to get it (doesn't break windows or something). And make sure you don't leave difficult child outside in a hot car - dangerous for his health-but sometimes they refuse to leave the car adn the game. I had trouble handling that.
It doesn't have the same effect on Jessie and Tyler. They both stay grounded in reality, don't have fits when it is time to turn things off, etc...
If your husband won't help, can you make husband responsible for the difficult child stuff - all tantrums, use of anything with a screen, etc can only happen when husband is around to monitor and thenMAKE husband handle it by leaving it all up to him? Just back off and let husband see what it going on? May take a few months, it did here, but eventually even your husband would see the problem??