Sanding lead paint is not a good idea as the primary method of removal.
You should use a heat gun (below 400 degrees C as not to create fumes) to soften the paint and a scraper to remove the bulk of the paint.
Once you've done this you can use your RO 90 to remove the remainder that wouldn't come off with heat, but make sure you have your Rotex hooked up to an extractor with a HEPA filter, (preferably a class M but a class L should be ok if it's a small one off job), wear a good quality organic vapour mask.
As for the correct abrasive, it depends on what you're finishing with. If simply painting with white gloss, latex, etc then it will hide a multitude of sins and you can get away with a fairly coarse abrasive. If staining then you'll need to work through the grits to get a quality finish like you would usually do. The actual abrasive type doesn't really matter, brilliant 2 or Rubin 2 would suffice.