I don't know what the relationship is like with your Mum and Step father, but at 19, you are supposed to be capable of leaving home.
Though it's by no means easy, previous generations were all leaving home far sooner than they seem to do these days.
I totally disagree with you about the 'different world out there' attitude, as it's always been a 'different world' for every single generation.
Working at 1 part-time job at the weekend only probably won't earn you enough to get a place of your own, but there's nothing stopping you getting another part-time job in the evenings e.g as bar staff or waiting staff etc.
Working 2 part-time jobs would earn you enough to get a room in a house share with other students.
Loads of students expect their parents to continue to 'fund' them, simply because they are 'students', but there's nothing stopping you from working more than weekends. Saying that you need the evenings to 'study' is not true, you can study whenever you have some free time e.g for 2hrs after college before your job starts + after work + weekend evenings etc.
You can do it, even if you need to 'study' in short blocks (which is actually a more effective method as long blocks of study are less productive)
I personally worked 3 jobs while I was at Uni so I could afford to not live with my parents. It gave me new friends, a varied social life and an appreciation of hard work paying dividends for me.
It's horrible if you feel 'pushed out' of your home, but you are an adult now, so maybe it's time to take on the responsibility of housing yourself.