Okay, this once again is a lot to unpack.
Algae planet finally answers your "Where da food" question. They needed the horrible algae paste because the prior food supply was contaminated somehow. It is not in fact, poop.
New Caprica DID produce food, and had what stargate likes to call "Space deer". Which are regular deer, but we're on another planet. Hence, Space deer.
New Caprica was mostly a very cold inhospitable place, but it had a temperate zone near the equator, which is where they colonized. We know that farming was fairly easy in this zone, as explained when Admiral Adama and Former President Roslin smoked a doob. The network got super pissed about that scene. I don't see why, it's not like they're smoking anything illegal, after all, it's an Alien Planet, and they're not American.
A lot of the farming equipment was left behind on New Caprica, so they're in bad shape wherever they end up. They were on New Caprica for one year and six months.
The eye of Jupiter is, I guess, the last rest stop? Remember how the chief talked about the religious significance, and that scripture said it was going to be destroyed, and then it blew up?
The final five cylons do not in fact, know that they are cylons. Cavil wiped all memory of them after he killed off one of the models. They are in fact, the first cylons.
The future cold storage cylon is not any of those things. She's "The hybrid" essentially, every cylon basestar has one. She's like the central computer. You may notice her ramblings resemble maintenance schedules.
So the food supply is now finite. The algae planet was destined to blow up. We now know that the supposed scripture is in fact, a script. The colonials are being led down a path. This is not necessarily a good path. Their gods are huge assholes.
That's actually something they already knew, but chose to ignore.
According to their scripture, the 12 colonies of Kobol were colonized after the gods did something so bless'ed terrible, they doomed themselves, and sent off the colonials in 13 ships. One vanished, creating the myth of the 13th tribe, also called "Earth".
Their home was known as Kobol, but they were NEVER supposed to return, under a threat of a blood price. Which in the show was literal. Every ship that landed lost at least one person.
So now they're looking for earth to make it their new home.
I do find it interesting, and a bit of a cop-out that RDM never explained what it was that the gods did that was so terrible.