Help with sound dampening

I have found that this new mess tape that has sticky stuff to stick to the wall seems to not hold very well. I applied the tape and then covered with general purpose mud...did the normal 3 or 4 layers and it was very hard to get it to lay down. I also use some of those paper and plastic outside corner and glued them on before using mud. They did not seem to hold very well either. What could be the problem?

I have a family room that is not in the ground but I have a 5' heigh concrete block wall with wood studs then 1/2" sheet rock. I want to take out the sheet rock and drylock the wall and then insulate and then add new 1/2" blue board sheet rock. I think that would be the best down there, it dose get damp down there. I was thinking of going with 5/8" but not shore if I should? The other problem is I have hot water baseboard heats down both sides of the walls, that are from 1963, There not the noraml small size there a little bigger. My question is do I just cut the old dry wall to the top of them and replace from there up or replace all the way down. I would like to do it right and replace all the way down but I have no idea how to remove the old baseboards? How is it down and can it be done with out remove the pipes and fins? thanks