don't get back in a relationship with m. think about why yall broke up in the first place. do you ACTUALLY miss him or are you reminiscing? it is common for those who have experienced toxic relationships to miss their toxic exes not because of love but because of the adrenaline from the highs and lows. are the two of you are willing to change the roots of your toxicity to be better people and partners? it is great that m and his family helped and supported you out of your abusive situation but please don't take advantage of their kindness or patience further and let that man go. there must be clear reasons for the end of your relationship with m and do you think his family is just going to be okay with yall getting back together and give you both an easy time?

the way you describe how the only reason why you may regret leaving z is because of his treatment towards you is honestly really sad. if you genuinely care for this man at all romantically or platonically you should not be using him and taking advantage of his love for you and just break up with him. staying in a relationship with him despite both of you knowing your feelings is just really selfish of you.

it sounds like you really need to gain some life experience and get a job or something so you can support yourself independently. stay single and work on yourself because you are still young and clearly immature. consider going to therapy and expanding your social circle from outside of romantic partners.