It may be slightly easier to find evidence of your father's appearance in front of a congressional committee during the 1950s, as this will be in published transcripts of congressional hearings, rather than archival material. Any major library in your area that collects government documents (university libraries are a good bet, and should be happy to help you) should be able to provide you with the CIS U.S. Congressional Committee Hearings Index, 1833-1969. This index is searchable by names of committee hearing witnesses, which should include your father. Details about searching congressional hearing records are provided by the National Archive's Center for Legislative Archives "Guide to the Records of the U.S. House of Representatives at the National Archives, 1789-1989 (Record Group 233)", chapter 1, paragraph 1.108.

In terms of hunting down your father's articles in the Daily Californian: if you are in the Bay area, it might be worth a visit to the Bancroft Library at UC Berkeley. They house the archives of the Daily Californian, including the papers from the early 1930s. You can find information about the Daily Californian archives (housed within "University of California, Office of the President records, 1914-1958") in the Online Archive of California's finding aid for these papers.

Unfortunately, these archives are not digitized, so you would either have to visit or make arrangements with the Bancroft library to have items found and copied (sometimes possible for a fee.)

I hope this helps to answer your question - please get back in touch if not.