Can excessive gas and bloating cause an existing hernia to push through and continue to push back out after pushing back in until the gas passes?

Yes. If there is bowel in or near hernia sac it is totally possible the dissension of bowel will make hernia more pronounced. Danger is if bowel becomes trapped and dissension cannot be relieved then bowel can can be damaged and cause life threatening problems. Hernia should be evaluated by an experienced surgeon to determine the risk of fixing versus not repairing.