I don't know about auto techs but I do know about the sort of situation that you are describing and reasons for your concern. I don't think another wife of an auto tech that works somewhere else can be of much help for you in knowing what is going on with your husband.
Even if he's up front and working late hours I suggest that your anxiety about it is reason enough to find a way to develop better communication with your husband. Have you talked with him about your fears in a questioning, non-judgmental manner? If not, I suggest that is the first step for you. If you've tried discussing it and do not feel that he understands, now is the time for some marriage counseling.
By understanding, I mean does he understand how you feel and is willing to find ways to reassure you? Does he understand how difficult being at home all those hours without him is difficult for you? Are the two of you able to think together to find ways to make the situation better for you?
Off the subject but perhaps helpful is the suggestion to find a mother's helper. Perhaps a young neighbor girl who would come in and play with your son while you're at home to give you some time for yourself or to fix dinner. I may take time to transition your son to being comfortable with someone else but doing this will be well worth it for both your and your son's sake. At 2 he should be able to be self-sufficient enough for you to fix dinner.
Have you tried putting him a high chair in the kitchen while you cook? I think that if you develop a life for yourself that you'll be less concerned about the hours your husband works and your husband will want to be home more.
I would understand that he might, even unconsciously, choose to remain at work. Is it possible that he's having difficulty handling yours and your father's neediness? It sounds like you depend on your husband for everything including the ability to fix dinner.
You don't say what your handicap is. Does it mean that you can't get out and about and make friends for yourself and have play dates for your son?
My father was rarely home. He owned his own business for many years but even when he worked for someone else as an appliance repairman he stayed after hours to continue working. I know he was working because we kids would stop in to visit. I strongly believe that his work was much more satisfying to him then being at home with his mostly unhappy wife who frequently complained about his not being home but didn't work to make it pleasant when he did come home.
If I were you I would focus on making my own life more interesting and see what happened for myself. We can't change anyone but ourselves. I would be anxious and scared if I had the life you have described here. I might start with talking with my doctor about taking an anti-anxiety and/or antidepressant. I would find a way to get out of the house with my son. Go to the park, library, even the mall and people watch. I talk with people where ever I am. When I'm getting anxious I get out of the house.
If you've not done any of this it will be difficult to get started but reach out and find a way to make friends and develop a life outside of your home. Perhaps start with a mother's helper so that you can learn how to be independent from your son and him from you.
My heart goes out to you. Your life now, as you describe it, must be painful. You can make it better.