Ah, ok, you mean in the Dungeon tools, the CUT WALL feature.
I need to first ask. Is the wall you are cutting a Singe Line with a thickness applied or is it a MutliPoly. The cut feature only works on a single line (regardless of thickness).
Your second problem is simple actually, copy the floor to the wall layer & sheet. Then hide all Layers/Sheets but the Wall. Select the now copied floor poly, and change thickness of the line and color and fill and Viola! A wall in the same shape.
For added goodness, you could instead of changing the line thickness, draw a box around the whole, and then multi poly the two together to make the wall a solid object with a 'hole' in the centre.