My condolences, it’s hard to lose a fish. Most people think it’s stupid to be upset over a fish but it’s not, I mourned for weeks. I also considered leaving the hobby because of it. But just try and hold on... I encourage you to get a new heater and keep up with your weekly water changes. Maybe do the minimum for now and in a while I promise you, you’ll want to get back in it again. And a while probably isn’t as far away as you think. I’m not sure what heater you had but I’m using an Eheim Jager I used it on a forty gallon and now a twenty gallon and it works amazing and I haven’t had an issue so far... I don’t even have an ink bird on it. Maybe you might wanna try one of those out?
And you’re obviously an amazing reefer, you’re the youngest reefer I’ve ever met and I mean you catch lobsters to pay for your stuff... you’ve got a passion for it. Just hold tight bro, things will get better. Without the lows in this hobby we’ll never get the highs.
EDIT: I saw your tank is an AIO have you put a light in one of the back compartments? It helps centralize algae growth back there and not in your tank. That’s what I’m doing... I get the little bit of algae here and there in the display but nothing terrible. The back compartment looks like I stuffed the grinch in it it’s so full of GHA.