Notice that in your calculations for rounding, you have the decimal specified at two places:
round(numbers....numbers,2)
If you use that, then round(amount/4 * 1.5,2) = 1.5 (where amount == 4)
For your sample problem with the new math tools, you could say:
<$text text={{{ [{!!amount}divide[0.5]multiply[1]] }}} />
The <$text.../> widget makes it come out as text. Yes, it would be useful if there was a filter operator that would make the result not be a link.
Hmm. You could put a style on the page so that the links no longer looked like links.
HTH!