I cant get fine enough adjustment t in Engrave mode to make these brackets line up exactly [It becomes very apparent at high magnifications but I can see it at normal size]. Currently it looks sloppy. Is there a micro-adjustment or align mode in engrave mode that I don’t know about?

Yes there is: if you over with your mouse over the value in the Panel, you will see that Dorico translates the fraction number in a decimal number and shows it in a little white overlay. Remember what it is and write in the box the desired value as decimal number increasing or decreasing it in a very fine way.

In my example, writing 0.16 (instead of 0.13 , that was the nearest value I obtained with alt+arrow up) aligned exactly the point with the previous tuplet. Repeat for the desired points.
You will also notice that Dorico translates your input into a fraction: so 0.16 becomes 4/25.