In answer to the uniform question, The best thing is if you can find some photos of him and try to depict what you see.
There are a lot of different orders of dress you could do him in. For working dress, I'd go with either HBT cover alls or with the two piece work suit. Either would be OK. For a cap there is the daisey may (Dragon has done them and included them in their USMC carded sets. Kinda hard to find and they need some tweeking to look good.) The other cap choice was the engineer style cap (similar to the USMC cover Dragon has done)
The best one I've found is the cap that comes with the Gear Box toys HBT set. The shape is great, no one seems to really do the right fabric.
Some other choices for the Philippines: Use the tan uniform that came with Dragon's Jack Sullivan. Battle gear toys does some over seas caps which will go along good with it.I don't know if the offer them in Air corp blue and yellow piping, you may have to customize that part. Or if he is an early or even pre war figure, give him a Battle gear toys campaign hat. (For that From here to Eternity look)
If you are depicting him on an airbase,you will want to stencil his rank on to his HBT's, he would wear the standard embroidered rank stripes on his tan uniform. (stripes should be white three with one rocker for S/Sgt)
One more note about caps. Checking images online I see that with the Air Corp there is also a lot of examples of guys wearing what looks like a tan ball cap. It has a low crown and a long bill. I don't know if these were issued or something guys just bought and wore.
So there you go, probably too much information, but I hope some of it helps.
Tim