To average 100 miles per day, I'd expect you'll have to make up some miles in the middle to accommodate shortfalls in the mountains at either side of the country. Washington Hwy. 20, for instance, there are certain places that are reasonable to stop, with large gaps in between. So you may need to average 110-125 in the plains to make up for that.
Are you willing to consider backup-plans? For instance, if you're running out of time and have 14 days to complete 2100 miles (although you'll probably notice earlier), what will you do? If you're heading east, will you consider stopping in Cleveland and flying home from there? Although you may not want to plan it now, it may well be a good idea to have a concept in mind in case illness, mechanical, or just bad weather delays you.
Further, have you thought about completing a cross-country/Northern Tier ride in sections? For instance, there are several Appalachian Trail hikers who've completed the hike over 5-20 years, taking 2 weeks' vacation and hiking another segment each year. You could comfortably complete 1/2 to 2/3 of the NT this year, and then come back in a year or two and complete the rest. I'd give you better odds of completion if you were aiming for 75 miles per day (which is a whole lot of miles per month), and planning to recover from a few bad days along the way (Pete's half days, or zero days, whichever is more appropriate).