I would not jack on the middle of the sub-frame and especially not on the rear axle.
You mentioned earlier the brake fluid being very toxic ... I would never drink brake fluid, but I never avoided skin contact ... as long as a soap and water wash was to follow soon. But I would not want to submerge any part on me in it either ... just never been that concerned about a little casual contact. I may be living dangerously/carelessly and did not know it.