How can a ring oscillator work without burning?
red node at Voh + Vih (5 + 3.2 = 8.2 V) which is much
higher than allowed from datasheet.

Resistors R1 and R2 restrict the current that can flow into the TTL output and input nodes. It won't burn. Input current is limited to much lower than the 1 mA limit specified in the data sheet. It can't happen. I mean, why else would R2 be present. The internal protection diodes are perfectly adequate with such a small current injection.