What is a safe time gap between full-mouth x-rays performed in a dental office and panoramic x-rays in oral surgeon office? my concern is amount of radiation?

For both procedures the total amount of radiation is much less than the radiation of a CT of the head so you do not have to worry much.

No worries. Radiation is minimal, and the chances of developing health issues before your turn 100 are virtually zero.

Different diagnostic tests. FMXR shows cavities, bone levels. Panorex shows surrounding jaw bones. Total radiation less than you would get during a long airplane flight, or a day in the mountains, or 2 days on the beach. Your doctors can't work blind.