When Jasper jumps into the river to save Octavia he is soaking wet, but he should be completely dry as he had not been in the water yet.
Once the 100 landed on Earth, in the first 5 minutes, Clark's hair goes from looking like it hasn't been washed in a week, to just came out of a beauty saloon.
After it starts to rain, Dr. Eric Jackson tells Abby that the 100's plasma osmolarity is going up across the board. Abby says this must mean they've found water. Increased plasma osmolarity would actually mean they were more dehydrated, decreased osmolarity indicates increased water consumption.
When a spacecraft is re-entering Earth's atmosphere, passengers are not weightless and cannot "float." Astronauts actually experience the highest g-forces of the entire mission during re-entry, before the parachute opens, as the spacecraft decelerates from orbital speeds to about 200 mph in only a few minutes.
When they see trees and flowers glowing in the night, they are amazed and appreciate that. Well, trees and flowers are not supposed to glow, if they are glowing, it means they got mutated by radiation, so there is excessive radiation that would be harmful to humans, they should have gone far away from that place, opposite of going near to it.
Councilor Kane gets Dr. Griffin arrested and sentences her for summary execution for having administered anesthesia more than the limit prescribed in the law. It is a doctor's privilege and discretion to decide, on the run and on a case to case basis, what dose could be suitable for a particular patient. There just can not be a law prescribing maximum doses of each and every possible artificial or natural chemical that can be administered.
The 197 years until a safe return to Earth time frame is ridiculous;
since, for example, the radiation fallout from the 1986 Chernobyl disaster is expected to make the affected areas uninhabitable for at least 20,000 years.
However, it actually depends on the amount of radiation, and that will depend on where exactly the nuclear missiles had struck 100 years ago. The radiation would be higher at the point of blast and would taper out as we go away, and it would be minimal or none at all at faraway places or secluded places. Taking example of real life happenings, Hiroshima and Nagasaki have been rebuilt and are thriving and it is not even 100 years yet.
When it is raining, one guy suggests they have to collect the rainwater. Well, they saw a river or a big pool having lots of water, that had dangerous man eating animals, but water should be nonetheless safe not just for swimming, but for drinking also, so there was no need to take pains to collect rain water.
When Octavia is spinning around the tree, it can be clearly seen that the bark around the tree has been scrapped off intentionally around the spot where Octavia's hand is so that her hand doesn't grip the tree and instead slides smoothly around it. When the camera is showing the backside of the tree, the part her hand touches is visibly worn down, and in some spots, through the bark.
After Jasper has swung across the river and Finn is holding the "vine" rope, you can clearly see that it is a standard 3-strand manila rope with some vines added to make it look like they made it themselves.
When Finn is swinging on a jungle vine. White cable ties can be clearly seen holding it together.
How could they sent the 100 to the Earth without any supplies at all? They could have filled food and other necessities for a few days at least, to last till the 100 found the supplies on Mount Weather on Earth. Also, as they were being sent to a planet whose current status is not at all known, they should also have packed enough firearms and other equipment so that the 100 could counter any attacks of dangerous animals.