Military here and I easily work 12-14 hours a day; longer on some days. I don't mean to come off as condescending or send a "stfu and man up" vibe, but sometimes that's what it takes. It seems like you have a good head in between your shoulders, so that's good. Fuck a New Year's Resolution. Fitness ain't something you do for a little while and quit. It's a lifestyle. Actually, make fitness yo bitch and make it a part of your lifestyle. Juggling a physically demanding job and a fit lifestyle is hard, I know. Especially when you're just starting out but after a few weeks your body will start to adjust. I don't know how old you are, but as a 22 year old, its easier for me to say and do (assuming you're older than I with kids/family/etc), so I'll give you credit in that it's tougher for you than I. But I will tell you that adjusting to a fitter lifestyle will be easier if you ease into it. Baby steps, baby... baby steps. Doing too many things all at once is setting yourself up for failure. I'm reading that you're changing your dieting habits and cutting out nicotine. That's superb. Now that you've got the hang of those, why don't you try counting calories as your next "step"? I've lost an incredible amount of weight by counting calories alone. Once you get the hang of that, you'll want some muscles, so look up some tried and true fitness programs!
With your job situation and limited time, I'd suggest you look up some bodyweight fitness programs. Now, I personally don't do any bodyweight training (because I do enough of that at work) myself, so I don't have any specific recommendations, but I do have buddies that do and have gotten great results. The beauty of bodyweight fitness is that you won't need any special equipment and you can do it right at home or work. Maybe you can look up a program and spread it out throughout the day. Sneak in some planks, push ups or pull ups here and there. Also, mastering your bodyweight is a huge plus. There's a dedicated subreddit for it too: /r/bodyweightfitness.
If you have access to a gym, look up (you guessed it Fittitors) Starting Strength. Only 3 sessions a week, 45 minutes tops, if that. Starting with the bar should help you adjust to it as well. No gym easily accessible to you? You're in luck. The only special equipment you'll need will be a squat cage/rack, barbell and some weights. With a little bit of your time 3 days a week and an on-point diet, you'll be making solid progress in a very short period of time.
PM me if you have any questions, I'll be glad to answer your questions to the best of my abilities.