First off, my issue is in the front as the rear heater works as intended.
I have not only just slightly warm air coming out (warmer if I give it gas) but it barely blows at all no matter what setting 1-5. It sounds like the air is trapped In the dash. (No issues with the AC)
I checked the actuators and they are working. I noticed yesterday that if I turn everything off it sounds as if the blend door is opening and closing still at random (I heard it maybe 4 times during a 10 minute drive, not aure if that is what the sound is, as it sounded close to the floorboard or deep in the dash) and I still get cold air blowing through vents as if the AC is on.
I also have noticed a vibration and sometimes a light thumping noise that sounds like Its coming from under the hood when im at a complete stop (nothing in park,reverse...). My temp gauge fluctuates here and there as well. It never overheats though, it goes maybe a quarter of the water towards hot from the center). Nee thermostat, water pump and the radiators been flushed. I know that someti, es the ac can cause issues elsewhere somi figured this may be at least a little relevant.

Im thinking maybe the heater core needs to be replaced but am honestly not 100% positive and I also am not really looking forward to it as in seems like it's going to be a royal pain in the butt. Could there be a possibility of a clog, if so how would I go about flushing it?

I swear gm purposely made everything in these vans nearly impossible to work on.

Thank you for your help in advance,
One very frustrated mommy.