V2005 Volvo s40 vehicle has no heat

Hi, I'm looking for some advice on how to fix my no heat issue. Ever since I've had the car its had mediocre heat, but now it's just cold. Sometimes if I rev the engine it gets warm, but not as hot as it should be.

Lat night, I flushed the system with water a few times, and used a chemical flush. I drove it with the water & flush in it for a few hours, and it had good heat, regardless of engine speed. I did overfill the coolant overflow a bit though, not sure if that makes any difference.

After I drained the chemical flush out and put the correct amount of coolant back in, I'm back to the same issue, except a little worse. I have pretty much zero heat regardless of engine speed. I hooked a scan tool up, and the CTS is reporting around 180F, but occasionally as hot as 225F. Temp gauge happily stays at operating temperature

With the flush in the system, the radiator hoses felt like a fully inflated tire. I could hardly squish them. With coolant, they're often lukewarm and easy to squish. If I squeeze them a few times, they get hot but only for a few minutes before returning to lukewarm. Top heater core hose is hot, bottom is cold.

I try bleeding air out of the cooling system, but the coolant boils before I can get all the air out. I put the cap back on before any can come out. Any advice? TIA