So sick of crappy landlords

I swear no matter where we move out landlords suck. Old place let the roof get so bad it caused a hole and water damage in our room. Now here our new place sink is leaking. It happens if we run the dishwasher or use it. Started as a small leak and now it's huge. We keep a bucket under it but the moisture is messing up the wood and starting to mold. We bleach it but I know that only helps so much. It will need to be treated. I see this issue a lot with Rv's and do the warranty work I know this small leak was only a couple hundred to fix but now where talking at least 500+. Also now our pilot is going out on the heater and will run without putting out any heat. I've called the landlord, texted and emailed. He said he'll send someone out but never set a time or day. Now I'm going to mail a letter by certified mail. Not sure what else to do. I could withhold rent because both are heath hazards but that's tricky being in a month to month. We plan to start looking at homes to buy here next April. Still that's a long time to have these issue's. Any advice would be awesome.