Rotorspeed, as for your first question, I'm sorry but I can't answer it. We can't begin an approach with less than 1/4 mile visibility, so that's the lowest I've landed with. With 1/4 mile vis, the approach lights usually become visible at or just over 200', and the REILs and PAPI become visible at or just over 100' - at least that has been my experience.
IME the lights are easier to see at night, without refracted sunlight masking them. If I have to fly an ILS down to minimums, I prefer to do it at night, because I think I have a better chance of landing. Also IME, if you can't keep both needles centered, then keep the localizer centered if you can. If you're a little high on the GS you'll still be able to find the runway if you're over it.