The secondary is low in PH, low in nutrients, high in bacteria competitors (the yeast colony) and high in alcool. It is not an easy place for bacteria to spread, but sanitizing is always a good procedure.
Could be an infection, but it could be a part of the final fermentation as well. I suggest to leave it alone for some days and see. If the mold becomes furry it is definitly gone
You remind me a dark belgian batch that I made some years ago with a friend of mine. The fermentation smell was very strong and I thought it was gone. The friend of mine convinced me to proceed and to bottle anyway. It turned out it was fine.