Barney is seen driving many times and getting speeding tickets, yet according to Arrivederci, Fiero (2007), Barney never learned how to drive because he's too scared. But he could have learned to drive between then and now.
In Season 4, Stella tells Ted that she got pregnant when she was 19 and has spent all her time since then (5 or 6 years) devoted to being a single mother. However, if Stella had given birth when she was 19 or 20, she would not have been able to complete medical school, become a dermatologist, and have her own reputable practice by the age of 24 or 25. It takes 8 years to complete medical school and 4 years to get a bachelor's degree. Stella would have been a freshman or sophomore in college when she got pregnant.
Tony is trying to make amends to Ted for destroying his relationship with Stella. This is contradictory to Tony writing "The Wedding Bride", which totally trashes Ted.