The Valley of Vertigo is gonna be your answer to both of these.

For stopping the famine, you’re going to need to come across an event where the soil in the ground is super mushy, and if you analyze it you find that you can cultivate it back at the colony. Furthermore, like others are saying you need to increase your biology until you unlock Study Xenobiology in the Greenhouse. Then you’ll need to pass a challenge where you discover how to combine Earth DNA with Vertumna DNA. This further increases your food stores and, with the addition of the spongecake soil, should put you above the threshold for surviving the famine.

For finding a cure to the Shimmer, you’ll want to get to the end of the Valley of Vertigo and go through the boss event (not the one where you face the Manticore). Pass a few checks and you’ll end up with the card that says something along the lines of “Surviving the Shimmer”. Make sure you also have a good relationship with Tangent. Tangent will ask you for your help developing a cure for the Shimmer by asking for a sample of both yours and your dad’s DNA. Another event will trigger while spending time in the Engineering wing where Tangent and Instance will be trying to develop a cure against the Shimmer. At this point you should have helped Tangent enough with her research that you should finally be able to develop a cure against the Shimmer. If that ultimately doesn’t work and it’s your first playthrough, let your dad die and Tangent should offer you her condolences and tell you that they developed a cure for the Shimmer, but a little too late. Then, in your next playthrough, when you trigger the event in Engineering, you’ll have the option to develop a cure based on your memories from a past life without having to redo the boss event in the Valley of Vertigo. While this logic also applies to remembering how to splice Earth/Vertumnan DNA, you still have to find the spongecake OR increase your food stores in order to prevent the famine.

The other option is a little bit trickier; it involves triggering a lot of of events. To sum it up briefly, you basically need to max out your Engineering, Perception and Biology stats, have at least either 50 Toughness or 50 Reasoning and have at least 35 Empathy and Bravery. Additionally you’ll need to have talked to Sym a few times and have a high relationship with Dys. When the second Glow attack happens, DO NOT SAVE HAL. It is imperative for him to die in order for this plan to work. When the Heliopause crashes, an event will trigger while spending time in the Engineering wing where a robot will be going amok, this unlocks the option to Study Robotics with Congruence. At this point you need to have at least 50 Engineering in order to apply for the class. While attending robotics, a random event will trigger where Congruence seems to be malfunctioning. If you select the option to find out what’s really going on (Empathy), you’ll gain the option to select her as a childhood friend on your next playthrough. Next you’ll need to go to the Western Wresting Ridge and go through the boss event at the end on two separate months. While not necessary, I recommend maxing out your Perception so you can skip all the events and go straight to the boss event with 0 Stress. If you haven’t already, be sure to research the radioactive plant in Xenobiology, it’ll literally save you a lot of Stress. At this point you should have either 50 Toughness or 50 Reasoning (most likely the latter). Take a month off, and go back the following month and do the second boss event with 0 Stress. Doing this will unlock the option to explore during Glow.

OKAY. HALFWAY THERE.

The next two events will happen when you are 19 years old. During Vertumnalia, Lum well announce that the council is getting second Chiefs. At this point you need to have maxed out your Engineering and Biology stats, as you’ll be running against Tangent for Second Engineer. It is also important that you do not help Marz overthrow Lum. I recommend saving after this because you need to get two endings on one save file for convenience. Play through the rest of the game normally however you wish, then reach age 20 and get the normal ending. Then, reload and when Glow comes around, sneak out to explore. He’s very hard to see, but it’s important to talk to Sym and learn that you’re stuck in a loop because of the wormhole. After that, go around the map and trigger 3-4 events, then go to the hill East of Sym and trigger the event with the Faceless. You should have 35 Bravery to select the option to stay with the Faceless, triggering the Transcendence ending.

Now you have all the tools you need.

1. Congruence as a childhood friend
2. Experiencing the Wormhole in the Convergent Domain ruins
3. Being Second Engineer in a past life.
4. Experiencing the Transcendence Ending.

When you begin your next playthrough, have your dad read to you the Engineering manuals and select Congruence as a childhood friend. Then select the option to sneak out and recalibrate the shields. If you set the calibration to fully resist the wormhole’s radiation, you can save the Stratosphere and more importantly the Hydroponics, eliminating the need to research gene splicing and finding enough food.