There are 2 questions inside your question: which lens is sharp at f 2.8 and wider, and which is the lens that has the best balance of sharpness and speed in low light. The part of the question, which is missing, is the cost.
What we know, is that you want to shoot high speed film, so this means, that you need a lens, which is SHARP ENOUGH for film - this would rule out stuff like APO Summicron ASPH, a USD 7000 lens, which would be wasted in these circumstances.
First, you have some good f1.8-2.0 lenses, which are very sharp or just sharp enough wide open, and some are really cheap. You might have a look at the latest Nikkor 50/1.8 AFS, or even at the old Nikkor-H 50/2 or AiS 50/1.8. Then you have the Planar 50/2 ZM, and the Summicron M later versions, both tack sharp wide open, plus on a Leica you do not get the mirror slap, so the photos will be sharper anyway. Next level would be the Summilux M 50/1.4 ASPH, which is almost as sharp wide open, but is one stop faster - probably the best choice for the job, but costs around 4000 USD. Higher up, you only get the Noctilux 0.95, but I don't even know the current price, probably above 8000 USD.
A separate category would be some SLR f 1.2 lenses: the sharpest wide open is the Noct Nikkor 58/1.2, but is also picey - about 3000 USD, however, there are some lenses like the Minolta MD 58/1.2, which is not tack sharp at f 1.2, but is so by f 2.0, and anyway it gives you some extra margin when you really need it, the same goes for Pentax 50/1.2. These lenses go for about 400 USD.
Here's a shot with Rokkor 58/1.2 wide open:
201213022 by
mfogiel, on Flickr
and here at f 2.0
201213725 by
mfogiel, on Flickr