You can access it through get_ipython().config
:
get_ipython().config['IPythonWidget']['font_family']
Example:
In [1]: ip = get_ipython()
In [2]: ip.config
Out[2]:
{'IPKernelApp': {'connection_file': u'C:\\Users\\falsetru\\.ipython\\profile_default\\security\\kernel-7008.json',
'interrupt': 960,
'parent_appname': 'ipython-qtconsole',
'parent_handle': 956},
'IPythonWidget': {'font_family': u'Consolas'},
'ProfileDir': {},
'Session': {'key': u'4c0284b9-3a26-4989-b995-c930ab67bef5'}}
In [3]: ip.config['IPythonWidget']['font_family']
Out[3]: u'Consolas'