I need advice about what I should do about my job (Very long rant, I'm desperate for opinions)

So this is my first ever job and I have nothing to compare it to, therefore I don't know if his behaviour is normal. I started this job in the summer holidays and when I started he had a lot of patience and he was kind and a jokester. (I'm 17 turnings 18 in a month he's 26) But skip to now 6 months later things have changed drastically. My shift is easy I start at 7:30 am finish at 1 pm I used to work Mondays to Wednesday but since I'm back at school for my final year before university I only work Thursdays and Saturdays. a lot of things have happened on these 6 months, for example, he was robbed and they took over ten grand worth of cigarettes. I would always stay back and work extra hours for free and that became a natural thing for me to do over the last few months. he said I've been with him during the hardest time of his life and at the time I liked being with him and spending time with him when he was feeling down about it I would comfort him and do even more to help him. I would even come in on my days off. across from our shop a girl with a record shop, she's said to him that she's jealous of me and when I asked him why he said "she gets jealous of every female employee I've hired" I didn't care and I didn't think much of it she has a boyfriend after all anyway and he's my boss so I have no right to feel anything toward it. Then he started leaving the shop for hours at a time just to go visit her and talk, and I wasn't even on shift when he would do this. It annoyed me because he wouldn't even tell me and I had to serve customers and she would always be rude and give me nasty looks. I've been nothing but nice to her even taking her deliveries to her shop when she wasn't open to accept them (and these delivers were multiple heavy boxes) he's recently in the last 3 months decided to put his opinion on my friends saying what ones will fuck me over and my faults how I act differently with different people and that I'm a follower and don't think for myself that I talk too much, and I talk lots of shit I decided to change that about myself then he stated I entertain people who don't buy anything so I stopped talking to people and only spoke to people who were buying something. Then he said my customer service isn't good enough so then I began to be more engaging with customers. recently he took me to Manchester with him because I have never been before, he brought me food and we had a great time together. we would spend time outside of work a lot like Sundays when I would help him clean the shop (for free) or when I go cash and carry with him after work (for free). Then my friend would come to the shop long story short they would flirt, she was touchy on him he kissed her and I told them both don't do that because it puts me in an awkward situation. He blamed it on his "man urges" so I told him to keep the urges to himself. Recently I've had a hard time with my depression and anxiety and I even got kicked out of my mom's house and my grandad has passed he did comfort me through my grandad passing away and even said it was a good thing I left my moms because she's toxic and was bringing me down. However recently I feel like he's becoming more self-centred, not talking to me when I stay to help for free and even after school I would come to help him. My friends even tell me he makes them feel unwelcome at the shop and my family think he's taking advantage of me. He's a nice guy at times, and I've done a lot of mistakes and done things other bosses won't tolerate, but I feel like he's not appreciating the things I do for him and I know for a fact any other employee wouldn't do half the shit I do for him. Every time I'm in town I get him food or get him stuff he needs. I send parcels to post offices for him (for free) and I feel like I'm doing wife stuff when I'm nothing of the sort. And I only work for £5 an hour. I have no time for myself, school work, my social life, and I'm having breakdowns in the stock room I feel like it's all getting too much. I need help and opinions on what to do next. (also he's offered that I work every day until the 24th of December, I said no because it's my school break and my sister from uni is coming down) I tried to make a compromise and I said I'll work Mondays to Thursdays, however, he said: "If you don't do all the days then you don't do none of the days." I know this is a long rant but i really need help on what to do next.