I did speak to the vet for a while yesterday after work.
The tests basically show a perfectly healthy bird, except when he ran the antibody test for aspergillus, Gilbert has some antibodies present. (He has been exposed to the fungus somewhere without signs of infection, and my vet said I probably won't figure out when and where.)
Since he is back to being normal and all other tests show no sign of anything other than perfect health, the assumption is that he does not have aspergillosis, in spite of having antibodies. (He does not want to treat him and feels it's safer not to at this point.) He has normal CBC, normal weight, normal on the galactomannan test etc.
However he suggested possibly running all the tests again after a period of time (maybe not waiting for his annual but go in a few months).
With regard to the Xray--he said the only reason he isn't saying to do it is that such a small bird with "normal" blood test results, he thinks he will not see anything. But said he would not say not to do them either. (He will gladly do them if I choose, which I'm still considering having done, or possibly waiting a few months and running ALL tests including Xray).
I asked about my taking him out for walks and his spending a lot of time outdoors, asked if that increases his risks for sickness, etc. He seemed to think the opposite and that it is safe to have him 'out and about'.
While I was on the phone with vet, Gilbert was chattering away, trying to join the conversation. You would never know there was anything even slightly 'wrong' with him.
I was 'disappointed' to not have anything more black and white but my vet said 'you don't want to wish your bird has aspergillosis just to have a definite answer."