Welcome! i know all to well being married to a OTO trucker. 7 years was plenty.. and now i'm very happy he's a 'local' trucker.
Shop for yourself. Have a plan in place first (i.e. calorie counting, low carb, WW, JC, etc) and see if your inlaws would mind you keeping your own shelf of food in the fridge and pantry. When you are tempted by anything your inlaws bring in.. go do something else, like brush your teeth, (nothing taste good after that!) go for a walk, or get online and chat here!!!

This place is full of wonderful advice, and support. Use it to your advantage. Like you said, start out small... but try and tell yourself as much as you can stand, that you are worth the effort!!! Your marriage is worth the effort!!! No one can do this for you. You are WORTH IT!!!
Good luck on your weight loss adventure...