Hell, I've got nothing else to do, and I'm a pretty fast typist, so I'll take a shot at some of these. Hope it helps, and hope I don't screw it up due to it being late and me being tired. This being CC.com, I'm sure someone will let us know if I slip up.
1) I don't know of a good resource off the top of my head. It can be difficult to compare pictures of glaciers if you don't already know them, because they look very different at different times of the year, with different amounts of snow on them.
2) Tie-In Rock is not the summit of the mountain. It is a point pretty high up on the Cooper Spur ridge (about 8800' elevation) that is the traditional point where Cooper Spur transitions from a "hike" to a "climb". It is where the Spur gets much steeper, and beyond that point, it's climbers-only. Very hard to identify distinctly when covered with snow, as things are now. The ridge that had all the people you saw from the helo is a ridge that extends from the very summit toward the SE. Off the back (non-sunny) side of that ridge is the top of Cooper Spur.
3) The "Pearly Gates" are a couple of hundred feet below the actual summit. There's a fairly narrow (20'?) slot between the rocks that is the standard path up to the top from the south side route, but there are some alternate routes between the rocks, depending upon snow conditions. If you've been to the top of Hood before, it's pretty easy to find the correct route down through these. In bad visibility, and never having been there before, it would be hard. There was a very experienced group of Hood climbers that spent some quality time in a summit snow cave a few years ago, largely because they couldn't find the correct route down in bad conditions.
4) The strongest weather systems that hit the NW are those that come ripping basically straight onshore, west to east. This puts the standard south side route right in the teeth of those winds. The Cooper Spur side is normally, I suppose, sort of out of the worst of the wind. But that side is also therefore heavily at risk for avalanche danger because it's where lots of blown snow gets deposited. This blown snow could easily cover any tracks. In minutes.
5) The "normal" climbing season is late spring and early summer. Weather is better, and the snow is consolidated. A climb up Hood can vary between a seemingly very casual hike and, obviously, a brutally harsh, serious undertaking. Lots of people climb it every year with essentially no equipment. Not my way to do it, but some do. Even the easiest route has some moderately steep terrain, and all is well as long as you don't fall. Conditions can be really nice below, but icy above, and vice versa. One of the reasons people climb the mountain in varied seasons is to get experience with a wide array of conditions. You can camp out pretty much anywhere along the route (outside the ski areas), including the top if you're so inclined. Spending a night on top is not a rare thing for people to do in good weather.
6) A snow cave can be pretty cozy and toasty, albeit humid. If you've got protection from the moisture and coldish temps, you can live in one for a very long time, as long as you've got food and water. Especially water. Gotta have a way to get water. If it's pretty warm inside, you could theoretically drink dripping snow melt, but that's not enough. Best would be having a stove (and pot) to melt snow to drink, but obviously, you're then limited by stove fuel quantities. Any "desperate measures" (leaving a snow cave) taken by these guys is probably related to not having a way to get water, or related to realizing the onset of hypothermia, and knowing that they have to do something.
7) Anchors are indeed for going both up and down. "Going up" can suddenly turn into a "going down" if someone falls, and anchors are designed to hold one or more people if they fall. That 'Y' shape is pretty common for a snow anchor. I don't know if the alleged 'Y' that has been shown in pics is really their anchor, or something else, as Iain indicated. I'd probably trust Iain on this one. Anchors do often look sorta 'Y'ish because there are two pieces or equipment buried in the snow, and then there is rope or slings or something attached to the two pieces of equipment, and then they come together into a common attachment point on the downhill side. So really, it's typically more of a 'V' than a 'Y', but a 'Y' could work as well. If they want to lower themselves down the mountain (rappel), they run their rope through that common anchor attachment point so that it hangs from the center of the rope, hang off both strands of rope to descend, and then once reaching the end of the ropes, untie from it and pull on one end of the rope to bring it down to them. The anchor stuff up above, unfortunately, will have to stay there. If they want to repeat this lowering process, they'd have to build another anchor. Obviously, doing this over and over requires a lot of gear, and nobody carries that many pickets with them. There are other ways to build anchors in snow that don't require so much equipment, but the pickets thing is arguably easiest.
8) The anchors they would have probably built didn't have anything to do with rock. They were most likely snow anchors, probably built with what we call "pickets". These are typically about 2 feet long, made of aluminum, and with a 'T' cross section. You attach a strong sling to each one, bury them in the snow a little ways apart from each other, and then stomp down the snow over them. The snow ideally then gets kind of hard, and gets stronger than you'd ever believe. The slings extending from the pickets come to a common point, which is the main anchor point. In strong winds, I'd definitely create an anchor like this if I were going to be spending any time in one place standing up, such as working on a cave. That sort of anchor could also be used for lowering people down the slope, so any anchors they find up there could mean a couple of different things.
Maybe all this belongs in the Newbies forum, but it was asked here. OK, time for bed...