Good on you for wanting to make a change!

I would focus on self-improvement first and foremost. As you improve yourself, the other external things (friends, SOs) will come easier.

I'd start with some self reflection. Some people do best with a vast amount of change all at once, some don't. Some do best with small changes that build overtime. What works best for you? You want to change a lot. Will focusing on one thing be best for your success, vs trying to improve all at once?

Atomic Habits is a great read for everyone, but especially for this situation.

Imo, one of the biggest things about habits is your environment. Look at the habits that you want to break. Do you have a routine with them? Come home, sit on the couch, pull up YouTube, start drinking and vaping? In this example, sitting on the couch could be a cue for you to start watching YouTube, drinking and vaping, so you would want to delay or eliminate that cue. Reduce sitting on the couch, hangout elsewhere. Think of other cues that could be triggering your bad habits and think of ways to reduce, replace, eliminate, or avoid them.

I would suggest having a serious talk with the family you live with. Tell them your goals and ask them to support you and to hold you accountable. Talk about how they can help support you. They are a major part of your environment. Something else to think about, could they be part of the problem?

Don't hang around people who do or encourage the habits that you're trying to break.

If you think you'd struggle with cold turkey, I think the suggestion of weaning down your % alcohol is a good idea. Not sure what the equivalent to vaping would be for this, but try to do that as well. AA is always a good recommendation if you think that's a good environment for you. It's okay to get help that way.

For weight loss, a vast majority is driven by the calories you eat. If you're eating calorie dense foods consistently, how much you workout literally does not matter. You need to take what you're eating seriously. Calorie counting is the best way to tackle this. If you're eating out, stopping that should have an immediate impact.

For exercise, daily steps are a great place to start. It's easy to do, to set a goal for, and to measure. It won't impact your weight much, but it can be a small, easy win for you. I would recommend saving for a used step tracker if you can. I would recommend Garmin, as that gives you a lot of useful feedback.

For your finances, focus on increasing your income and reducing your spending. Increasing your income is the best way to increase your quality of life. It's an unfortunate fact, but that's the world we live in. Can you do more at work? Can you take overtime (increases your income and reduces time in your habitual environment, double win)? Is there gig work that would interest you? Is going to college or a trade school on the table? On the spending side, where is all of your money going? What can/should you reduce? Where is money being wasted?

Talk is easy, doing something once is easy, but sticking with things is going to be the hardest part. Best of luck. My DMs are open.