first thing I have to say is that I copy+pasted this in a google doc with times new roman size 12 and it made 5 pages. that's a lot. that's as long as the research paper I did on the entirety of Ireland. you just wrote an entire paper
second. you need to get Philo (and co.) to read some of this because you made some really good points on how Niche becomes too easy at a point and they could use this as ideas for Niche 2 if it becomes a real thing.
third. I'm glad you liked it so much! My thoughts into making the 2.0 were basically "it needs to be harder." Shorter lifespans (the first version's were way too long), a less skilled starter (always has deformed paw + runner's leg or velvet, and no horns), and longer pregnancy + kid days (longer pregnancy = less kids, and more kid days = more time for them to be vulnerable to birds and bearyenas since they can't run). I didn't know it was the perfect balance I like to make a rule that the tribe can't attack bearyenas for whatever reason, which makes it way harder since they have to spend a lot of time running, and since they always show up when there's a new baby, I have to sacrifice the baby or an adult to protect it. I'm more interested in it being really hard than making a story around it though, so it might be too hard for you to make a story with all that death.