I seem to have a version of python-hildon that should have the fix, so it's probably not that bug. But otherwise that would seem very likely.
On the Welcome to gPodder! screen, the buttons are thumb sized now, but not properly themed. I wonder what is up with that. Are those just standard buttons created with HILDON_SIZE_THUMB_HEIGHT, and you are not changing the widget name afterwards?
In the authentication dialog for my.gpodder:
As for getting pango compatible strings for logical fonts and colors, this should help: For colours, you should be able to get the GdkColor from a logical string with gtk_style_lookup_color() and then turn it into a pango compatible string with gdk_color_to_string(). For logical fonts, you can get the GtkStyle with gtk_rc_get_style_by_paths() (using the logical color name as widget_path), and pango_font_description_to_string() on the font-desc member of the style. None of this is confirmed or tested, but hopefully it will help you out.