Toilet overflows sometimes, bathtub completely clogged, large pipe in basement leaks from upstairs toilet or tub , I can't tell. Landlord says he will fix these things when we move?

That's the main waste stack... if that has to be replaced the house will be without any drains at all during the duration of the work... not sinks, no toilet, no tub, no shower.

Your landlord is required, by law to furnish you with a habitable place to live. He'll repair it after you move? UNACCAPTABLE! Inform your slumlord if he doesn't repair these problems ASAP you're calling both the Health Department and The Code Violation Department. Nobody should have to live like that. I'd also hold the rent back until the problems are repaired . Good luck, Tom