I see several inherrent problems in conducuting your search:
First, your posting reflects that he served up until 1943.The 100th BG website indicates that he was CAPTURED in JULY44.Your mother's suggestion that he was "hidden by a French family...until rescued" would indicate that he was returned to Allied control.The reference to him in the 100th BG database indicates he was CAPTURED 21JUL44.
If one were CAPTURED he would wind up in a POW camp.If RESCUED you are an EVADEE.---they are two different things.
The 21JUL44 mission was #166 and it shows NO aircraft or crews were lost.
Waticare was lost on 25APR44.Tail number was 42-38018 and fuselage code was XR-J.
She HasTa was lost on 29JUL44 Tail number was 42-107007 and fuselage code was EP-B. Mission was #170 to Meresburg. William Greiner--Pilot James Coccia--copilot
Mason and Dixon survived the war. It was tail code 42-31412 with fuselage code EP-G, and is listed RZI which means "Returned to Zone of the Interior"--with means USA.
There are two photos of JAMES R. RUSSELL on the 100th page.One shows him in the crew of CAUGHT IN THE DRAFT, and the other shows him with another unidentified airman and Russell is on crutches.
According to the 100th database, there were no other men named J. Russell in the organization.
If you could locate his Army Serial Number I might be able to apply that to a particular MACR which would have additional information for you.