Yep, you pretty much sum it up for me. I don't really have much to add... well what about the gel layer impact by the Spartan armor? I haven't seen any information relating to impact resistance by GEN2 armor, but judging by how more advanced it is it's most likely to be be nearly on-par with GEN1. This may be completely irrelevant, but I'm prone to going off on a limb like that. lol
For the most part, I've seen 5 different impacts in the games. There may be more though.
1. In Reach where Noble 6 was thrown from a Corvette, and landed on Reach. From the looks of things he sustained minimal damage besides a limp (maybe some other things as well), but by the time he enters New Alexandria he's fine.
2. In Halo 2, where Chief lands on the... ship thing (The Frigate's name escapes me) after arming the Covenant bomb. He acts perfectly fine after that.
3. In Halo 3, where Chief breaks off from the Forerunner Dreadnought, and crashes into an African jungle. From a concept art (and I think in game) it looks like Chief used a piece of metal to either A: Attempt to lessen the heat from entering orbit, or B: Actually using it as both a shield against the heat, and then again when landing. Unlike Noble 6, who's suit didn't lock up (from my knowledge), Chief's did. Presumably he was knocked out, but after his suit was unlocked he got up without any sign of fatigue. This does not mean he didn't sustain damage that we didn't see though.
4. In Halo 4, where after falling away from the FuD, he hits a piece of Ship Junk, and then proceeds to crash into Requiem's inner planet. From the look of it he got knocked out, but quickly got up like nothing happened.
5. Again in Halo 4. This time after the Didact was released. When the inner beacon/core/thing started to become unstable, he decide to jump for it, and land on the inner shell of the Planet (from what I remember). This time though you can see the impact actually caused a huge crater. Chief get's knocked out, but get's up afterward acting pretty normal.
Judging from these examples, and you're analysis of the Spartan IV armor, I think it's safe to say that GEN2 armor could probably hold up against a heavy impact. (sorry if some of this makes 0 sense, or if I sound like I disregard information you just posted. I tend to make things complicated real quick).
Welcome to the forums by the way!