Carefully read the section titled " 3. Outdoor Reset Operation:" on p42 (p45 in PDF pagination), and how to set up the curve in figure 8.6, using a user-defined reset curve. (preset 7 in table 8.7)
It looks like you set up the curve to deliver 160F water at an outdoor temp of +16F (which is about your 99% design temp), and deliver 120F water when it's 70F out (which is a bit much!) I suspect you'll never need more than 140F water @ +16F, and may not even need 130F water. With the curve as-is it'll be delivering ~140F output when it's 43F outside, a temp that would probably have you covered even at +16F.
Start by dropping the mild-weather output to 80F @ 65F outdoors and see if it short-cycles (probably won't, in a high mass system), and set the design temp output to 140F @ 16F outdoor. Hopefully it'll still keep up, but without overshooting on the warmer days.
If it turns out that it won't keep the house up to temp during cooler weather, raise the design temp up by 10F to 150F @ 16F and see how it makes out. If it fails to keep up, bump it another 10F on the design end. When you find the point were it keeps up, back off 5F, see if it continues to keep up, then ride it out for awhile. If it always keeps up, never overshoots or short-cycles during milder weather, you're golden.