Irma Glen (sometimes written as Irma Glynn.) She also worked at WENR. A 1938 radio schedule lists him on WENR as well. The two stations operated under a share time agreement from 1925 until they finally merged in 1954. More here.
The Uncle Mal program was carried on NBC Monday through Friday airing at 5:15 EST. the program was so popular he was able to publish branded collections of stories almost every year from 1939 to 1946. His titles included Tune-in Tales, Tune-in Again, Story Time, Little Lord Fauntleroy, Always New Tales, and others. The book The Encyclopedia of Old-Time Radio list him as variously active from 1931 - 1940.
According to an article in a 1939 issue of Radio Guide the program debuted in 1930. He began with ribaldly racist black face routines as the character "Spareribs" which he portrayed on both the WLS National Barn Dance and a lesser known program The Sinclaire Weiner Minstrels on WTMJ as early as 1932. Strangely the segue from black face to wholesome children's classics was gradual. When his children's began he actually did it in black face affecting the faux rural accent and all. More here.
The book The Hayloft Gang by Chad Berry even dedicated a few pages to the story of "Uncle Mal." Claire was known to emcee the National Barn dance in that era as well. The 1944 WLS Family Album indicated that Malcolm was also doing overnights from 3am to 5am in the morning. I am only aware of a single recording of his program in the Radio Gold Index making it a true rarity.