Dataset is not used as visualization. It merely shows it visually, but it is not intended for print or export. It shows it like this such as to give you a quick overview of your data. Not to refine and customize.
You can create a similar visualization using TableForm:
nds = Normal[Normal[Normal[ds]]];
labeltop = nds[[1, 2, All, 1]]
labelleft = nds[[All, 1]]
data = nds[[All, 2, All, 2]]
TableForm[data, TableHeadings -> {labelleft, labeltop}, TableAlignments -> Right]
or using Grid:
nds = Normal[Normal[Normal[ds]]];
labeltop = nds[[1, 2, All, 1]]
labelleft = nds[[All, 1]]
data = nds[[All, 2, All, 2]]
Grid[MapThread[Prepend, {Prepend[data, labeltop], Prepend[labelleft, ""]}], Frame -> True, Dividers -> {{True, True}, {True, True}}, Alignment -> Right]
giving:
