I have a block basement in the Midwest. The waterproofing paint works for awhile, but eventually fails in spots. The only real way to waterproof is from the outside. Yes, dig it up. Coat the outside. But painting the inside helps, but is not permanent. Good luck. I ran ac ducts down into the basement and scrapped the dehumidifier. ( Which is just an air conditioner the exhausts it's waste heat back into the same space. A dehumidifier heats the air that you need to cool to dehumidify.)