IHN = inositol hexaniacinate (the non-flushing niacin that DOES work).
With regard to the weather, I bet what you're feeling is barometric pressure pain. I get it any time the weather is making a strong change (up or down). In my case, it's definitely not arthritis, as I feel it deep within the muscles, down into the bone, but the pain isn't usually in the joints, as with arthritis. The ONLY thing that I have found to relieve that pain, which I discovered by accident recently, is chloride pushes (salt or potassium). I've never been able to get much pain relief from pain killers, and the only thing that gave comfort (but no real relief from the pain) was heat, heavy blankets (for the weight), and moving around (though definitely not restless leg syndrome ... I've been through the sleep studies to say so).
From my research on barometric pressure pain, doctors really DON'T know what causes it. I can't blame them there, and you'll see why in the rest of this paragraph. If it's in the joints, it probably is arthritis, but for many folks like me it's not. What they think is that the barometric pressure affects us on a CELLULAR level, too small for them to measure, which is why they can't say the cause. It's like the bends on a microscopic level.
Now, my theory as to why the chloride pushes work for me is that when a weather pressure front comes in, it's squeezing our cells, but because for some of us our the in and out flow from our cells is compromised (the cell membrane isn't allowing things back and forth as it should), our cells are squeezed with no where for the stuff inside to go ... like squeezing on a sealed balloon, the air wants out to equalize against the pressure but can't go out, so we feel like we want to "pop" (e.g., very painful). With the chloride push, it improves the transport through the cell membrane, allowing stuff out or in, so our cells are able to equalize against the barometric pressure.
I really feel for you. This past week for me has been very painful with the barometric pressure, worse so than usual, so I can imagine what it's been like for you. I'm sure you're probably already doing chloride pushes, but maybe you need more at these times?