With regards to the first expression, the 2 red brackets near the start suggest that you have not got a matching set of opening / closing brackets.
I've replaced your expression with a reference to the column() which actually contains the expression for the % calculation - which I reccommend you do too, as it makes it easier to see what's going on with complex conditionals like this. If it's the second expression then change it Column(2) etc
if([National]=' ' or [National] = 'Data gap', RGB(191,191,191),
if(Column(1)>[Target 85%] and Column(1)<[Target 95%],RGB(233,174,17)))))
Hope that helps,