20-09-2017, 09:09 PM
Stating the obvious but you do not mention, a few short sharp medium hammer blows on end may help shock free, or assist penetrant to enter. Heating to red weakens the stud but the loosening effect may compensate. By blowlamp I presume you mean the devices used by painters and in the past plumbers but these a bit unwieldly. Ditto heat guns. Cheap small torches running off tramper style canisters are available. Short nuts locked are seldom adequate