TTL voltage level? HELP!

You didn't quite read the chart in Section 29 correctly kg4wsv:

Input High Voltage, except XTAL1 and RESET pins

Condition:
VCC = 2.4V - 5.5V

VinHi Min = 0.6VCC

“Min.” means the lowest value where the pin is guaranteed to be read as high

0.6 * 5V = 3V.