The warlock uses the spell for himself and gets out of the painting. Later on the 3 sisters get out of the painting, while only Phoebe says it out loud. All 3 of them should have said the spell out loud to get out of the painting. Or at least they should have held each other.
After reading part of the Latin out loud, Prue says goodnight to her coworker. He says he will return the painting to the vault and see her tomorrow, then leaves the room without taking the painting.
Phoebe spent a few seconds writing on the paper yet there were about 20 sperm cells drawn.
Once Phoebe finds the words that need to be said to free the occupants of the painting, she wonders how to free her sisters without getting trapped herself. She then sends Kit into the painting with the words attached to her collar. There are two problems with this. First - Phoebe wouldn't have to worry about getting trapped since she knew how to get out. Second - No explanation is given for Kit getting into the painting, as she obviously couldn't say the words to get in, and if Phoebe said it she would get sucked in herself.
Dan asks Piper to help with Jenny's human reproduction project, then after Phoebe helps her he says he prefers she does her homework herself. He shouldn't have asked for help if he didn't want them to help her.
When Piper tells Phoebe "Don't do anything I wouldn't do", Phoebe replies with "Don't worry I won't..." which is to say she won't do any thing she wouldn't do then follows up with "you wouldn't cast a smart spell" which means she is going to do something Piper wouldn't do contradicting her statement to Piper.
Prue says that "Absolvo amitto, amplus brevis: semper mea" means "To free what is lost, say these words: mine forever".
But a literal translation would be: I release I dismiss, ample brief: always mine.