““Then I took off rad cap. Instant suction and collapse of both lower and upper hoses””
I think you may be misinterpreting what occured here… Suction and collapse of the hoses is contradictory. More than likely what you heard was Pressure…which when relieved allowed the Pumped Up and Ballooning hoses to relax and collapse.
Sounds like typical head gasket woes… It will pressurize the coolant system…forcing coolant out into the overflow…AND THEN…the head gasket Breach is leaking air and not allowing the subsequent suction effect of when the hot coolant cools and shrinks in volume. This is what pulls the coolant back into the radiator and when there is an air leak as in Head Gasket failure it will not allow this suction to form.
The head gasket will however allow cylinder compression to leak out into the coolant system…this is an easy thing to achieve with cylinder pressures being what they are. When this happens…well you know the rest. Textbook Head Gasket Failure