Without some pictures of the tree, it's impossible to answer your question about this particular tree. However, I can tell you that an 'old ' tree does not respond well to severe pruning. They are far less able to recuperate, much like elderly animals (including those of us of the human persuasion) .

I can also tell you that it is my understanding that galls made by citrus gall wasps should be pruned out as soon as they form and before the new wasp emerges from the gall. OR simply left alone.....trees can live for many years with galls.