At just over 2,500 feet, it's the highest point on the TMT. In spring, look for red currant blooming here. From Tom's Crossing, the West Tiger #2 Trail heads steeply uphill providing another way to reach that summit. Continue down the TMT on many switchbacks and, in about 0.3 mile, note the junction with the K3 Trail.
I rarely show up more than 1.5 ahead of time. Another idea: technically, the ticket counters usually open 24 hrs before your flight, and sometimes this is the only way to easily get special seats like exit rows.
The earlier that you arrive, the earlier that you can get to security and through to arrive at your gate. Frankly, arriving as soon as you can to O'Hare in advance of a flight is never a poor idea. Cutting things too close can ensure that you have a bad day and that you'll miss your flight. Arriving by 11:30am for a 2:20pm flight would not be too early..