To your last question first: I have the same question. This was on my mind when we went to Hell for Sure. When we got back to the Preserve, I told the ranger where we had gone and that we were interested in backpacking up there. He was enthusiastic about the idea, and when I filled in my permit to leave the car overnight in the Preserve, I put our itinerary down and his response was “sounds like a great trip.” So for logistics, I would just call the office and tell them what you want to do. They’ll send you a parking pass and gate code so you can get out if you return to your car after hours.
Our explorations in the area you describe were limited. We went to the base of Hell for Sure Falls only. We did that for a day hike and it’s about an 18 mile round trip. We were tempted to climb above it on the west ridge, but it wasn’t yet daylight savings time so we had to get back.
I can tell you that the Sinatra’s mother’s crash site is on the 10,000 foot ridge, but not exactly where. I went there with my dad about forty years ago, not too long after the crash. He was an SG wilderness ranger at that time and we lived at Horse Meadows during the summers.
As to getting in to Hell for Sure, Hikin’ Jim speaks of an old road that intersects the PCT. This intersection is about 5 miles from the Preserve, up and over a short pass and just passed the fork to Stone House. The road goes all the way to a saddle that overlooks the wash almost directly across from where the South Fork comes in and not too far below Hell for Sure canyon.
We took this route in to Hell for Sure the first time. My son spent time on google and had a clear sense of how it went. Apparently you can see it all very clearly from the satellite view. On the way back, however, we stopped where the old road leaves the canyon we were in, takes a turn to the north and switch backs up over a small summit before continuing on to the PCT. The canyon we were in looked like it would take us right back to near where PCT crosses the White Water at Red Dome. But it looked pretty brushy. We decided to risk it, knowing how “short cuts” often end up. But it was a dream. You end up in the wash that might as well be a road. We just stayed in the wash and wound our way easily back to PCT, cutting off the corner and two climbs.
So . . . for going out to Hell for Sure: (1) cross the WW at Red Dome and continue on PCT just until the very north end of the wash–right before PCT leaves the wash and heads up over the pass; (2) turn left up the wash and stay right against the hill; (3) wind through the wash always keeping to the right channel until you come to an old fence post with some rusted barbed wire; then take the left; (4) follow this wash up maybe a mile or so until you see a small knoll in front of you (looks maybe man made). The wash at one point comes very close to the knoll. The old road lies between the wash and knoll. It’s all pretty self explanatory from there.
Our main discovery about hiking in the wash is to stay in it. For me this was the opposite of my experience in the mountains, which generally tells me that traveling down in a drainage is harder. But in the wash, if it looks easy, go that way. If you can see 50 meters of smooth sailing, gobble them up and then look for the next clear path. Avoid the ridges and avoid vegetation. You will meander quite a bit, but the traveling is smooth and easy. Case in point: when we hit the main wash to Hell for Sure on our first trip after descending from the saddle on the old road, we tried to basically go up the middle of the wash, as it seemed the most direct way. This was difficult going. The second time, we got down in the gully on our right hand side (going up) and hugged the mountain. It’s smooth sailing basically up to Hell for Sure.
Hope this helps some and sorry I have no Beta on the ridges above Hell for Sure Falls, other than noting that the area looks very steep, dry, and brushy–what Hikin’ Jim called Two-Snake Hill, or something like that. Based on our experience, just be prepared to be denied time and again either cliffed-out or brushed-out. But we sort of like that.